Alton nods, “Okay, we’ll take the lantern that shows invisible things too.”

The shopkeeper smiles, and nods. 

So, to summarise:
You are selling the Potion of Radiant Resistance and a Potion of Stone Giant Strength for 1,300 gold.
You are buying the lantern that shows invisible things (300 gold), the cloak that makes you a bit harder to hit (850 gold), and the jade talking stones (400 gold) - total 1,550 gold

So you need to hand over the potions and an additional 250 gold total. Let me know who's contributing how much gold, and who takes each item.

They are a Cloak of Protection, Sending Stones and a Lantern of Revealing

Alton rummaged through one of his side pouches and begins to set coins on the counter, "Um... there's 138 gold pieces, 11 platinum pieces, and 20 silver pieces. That should cover the rest of the cost."

Yes, that's exactly right. And here are your purchases? Oh, would you like the colour of the cloak changing? (It's currently a deep blue).

The shopkeeper hands you the items. Another customer, a tall half-elf with long black hair walks into the shop and begins browsing.

Alton tucks the stones away in his backpack and picks up the lantern, "Do you want to hang on to the lantern, Silent?"

Silent accepts the lantern and immediately turns it on and shines it around the shop. 

(Edit: Just checked and realized I have no oil in my inventory so scratch that, I don't think he's able to turn on the lantern) 

Balassar just takes the cloak "No, this is a good color." he says swinging it around and putting it on. His gaze directing to the half-elf for a moment as they enter the store.

The lantern is full, so Silent is able to turn it on. It reveals no invisible objects nearby.

You will have to buy future refills yourself, so please keep an eye on how much you use, perhaps in the 'other possessions' tab of your character sheet.

The half-elf ignores Balassar, and he doesn't look familiar. His clothes suggest someone of moderate wealth but not someone important enough to be well known to the public.

The half-elf continues to browse, and the shopkeeper waits politely, in case you have any further questions. Outside, the city goes along its merry way, busy and offering many possibilities. You were on your way to Balassar's home, I believe - you can head there, or head anywhere else. :)

Silent has turned off the lantern and stowed it away. Well, good meeting you and doing business, Mr... ah... 

He offers a handshake to the shopkeeper and, after whatever words are exchanged between them to say goodbye, is ready to head to Balassar's place. 

Oh, err, Pumat, Pumat Sol. Did I not say? My sincere apologies, and please do come and visit again. Seems like you might finding all sorts of interesting things out there in your travels, and I'm always glad of a returning customer.

He shakes Silent's hand vigorously as the half-elf comes over to the counter. Ah yes, Master Dendrian, and how may I help you today?

Alton follows Silent and Balassar out of the shop, ready to go wherever. 

Outside, the street is busy; your cart is where you left it, perhaps surprisingly, but perhaps not - the Pentamarket is well guarded by the authorities, and you see Crownsguard and militia here and there, ever watchful.

Heading for Silverstone smithy then, lads? 

Balassar just nods as he begins to lead the group to his family smithy.

You take a turn, passing by the Victory Pit in the centre of the Pentamarket. Balassar, you hear the familiar barker's cries, announcing fights due to take place there in the evening each day this week. You don't recognise the names of any of the fighters. Outside is the great street market, the heart of the district and of business in Zadash, streets thronging with stalls selling many items - most of more interest to the homeowner than the adventurer, of varying qualities and prices, from all over the Dwendalian Empire, and some from the Menagerie Coast and perhaps further afield. If you want a spoon, or a hat, or an end table, this is the place to get it.

You turn down a quieter street, and up ahead Balassar can see the smithy where his family lives and works. It looks much as you left it - a solid, unshowy stone building which serves as a workshop, with your family's home on the floor above. A group of five children - humans, a half-elf and half-orc are playing a game in the street as you pass. The human's eyes grow wide as she sees you and clearly recognises you, though you don't know her; she whispers to her friends and they all run away down the street, past the smithy.

The door is open. You don't hear the sounds of hammer on metal at the moment, but you can see shapes moving inside. You are home.

Silent slows down as they pass the Victory Pit and takes a long look at the action before hastily catching up with the others. 

Once they reach Balassar's place he turns to him and says, You reckon we should wait out here? Let you catch up with your folks before we all barge in.  

Alton falls a bit behind at the stalls tailored for homeowners for a minute or two before catching back up saying, "My ma would have a field day back at those shops." He chuckles, "I can see pa standing behind her giving her grief but still letting her getting some of the things she wants." 

Balassar just looks at the people noting their reaction. As Silent asks his question he just smiles "Not at all, feel free to come in." with that he just comes to the open door and looks around "Father! Sister! You all home?" he asks walking through the door "I brought some friends with me."

You open the door and enter the shop front, where the buying and selling, rather than the actual working, takes place. A pair of dwarfs stand to one side of the room; they look like they might be bodyguards, but they don't seem nervous or concerned at your arrival. Nearer the centre of the room, a richly-dressed dwarf stands; she was clearly in conversation with the room's other inhabitant, and none too happy at being interrupted. She casts a cool eye in your direction, and turns back to Surina, your sister. Surina looks much as she has always done - perhaps a little smarter today than usual, her clothes tidier and better quality perhaps than you recall. She glances similarly at you, with a coolness that is rather surprising, and returns her focus to the dwarf. "My apologies, my lady. I do hope my brother's interruption hasn't annoyed you too much." 

"No, no, of course not," the dwarf replies. "Beside, I think we were largely done, were we not? I shall send over the materials, shall I?  And then please do visit with the first results, when they are ready to be inspected, won't you? I think two weeks is enough, isn't it?"

Surina nods formally, not quite a bow, and shows the dwarf woman out; her two guards go with her, stepping past you. Alton and Silent, standing behind in the street, you would see the three dwarfs exit, the leading one barely glancing as she moves between you and out to the city and the rest of the day's business.

Back inside, Surina folds her arms. The previously cool gaze is  now icy cold. "So," she says. "You're back."