Hi! I was thinking about playing a rogue with a few levels of druid to create a character who is a thief which has the ability the change into animals for mainly stealth and non-combat things. I could use some advice on what class or classes you think would be best to combine. If other classes are better, than I am open to suggestions :-)

Most of the features you need are part of your base classes, so choosing subclasses will depend on what extra features you want.

I think you've basically answered part of your own question, Crimlock.  Thief is a Rogue subclass.  Stuff like Second Story Work and Fast Hands are the kinds of abilities you would expect a cat burglar to have.  As for the Druid part, a Circle of Land or Circle of Dreams Druid would probably work best for the theme you want.  If you take Land Druid with Grassland or Coast background, you get special spells not on the typical Druid list that improve your stealth (Grassland) or your ability to get out of a jam (Coast).  If you like the idea of spells and an invisible Mage Hand cantrip, you might also consider taking Arcane Trickster instead of Thief for your subclass.  You get great utility either way.  

The Githyanki also get an invisible mage hand as a racial trait.

For official only material, Druid 2, Rogue X. Circle of Dreams at higher druid levels gives you great stealth and mobility options (6th and 10th levels). If you only want to go Druid 2, I would pick Circle of the Moon for better Wild Shape. For the rogue subclass, Inquisitive, Scout, or Thief would synergize the most.

If your DM is okay with Homebrew, I have a feat and a rogue subclass that might interest you.

The Obake rogue is based on the trickster spirit animals, like foxes. https://www.dndbeyond.com/subclasses/114155-obake

And the Shapshifter feat does a similar thing. https://www.dndbeyond.com/feats/125672-shapeshifter