Minions attuning to / using Magic Items (Command Words w/ non-speaking Minions)

So I have been taking it for granted that Familiars, Homunculus Servants, Steel Defenders can attune to up to 3x Magic Items each. However, do you put any limitations on this?

For example, do you let a familiar cast a spell from a Ring of Spell Storing? 

I often forget that familiars have like a 2 to 4 Int and that having a telepathic link does not mean you are conversing normally with them but instead it is more like talking to your dog (directly into his mind). I wonder how well my dog could learn to use a Magic Item as complex as a Ring of Spell Storing. Homunculus Servant is more like human-level Int so not as much of an issue there.

I had also been assuming that if a Familiar could not speak that it could NOT use a magic item with a command word. However, I recently became aware that command words could also be signed or triggered with a gesture (see below). Would you let a Familiar learn a hand sign or gesture to trigger a Magic Item with a command word? What if you had crafted that magic item? 

RAW- Command Word p220 - "A command word is a word or short phrase that must be spoken or signed for an item to work. Spoken command words must be audible and fail to work in areas where all sound is suppressed, as in the area of the Silence spell."