I'm curious on this.. Lets say for example you've got a tiny fox familiar, or a kitsune in fox form.
The Kitsune or Familiar is in one of your pouches and you become under the effects of invisibility.
Does this make the tiny creature you're carrying around instantly visible? Can that creature roll to hide in your invisible pouches? Does that creature become invisible as well, but only while riding in your invisible pouches?
I don't have a clue but it got me thinking of a particularly dirty barbarian going invisible and all you see in a nest of lice floating and head level and a few engorged ticks, all just seeming to hover along.
If the tiny creature becomes invisible it prompts the question: if the tiny creature attacks do both parties become visible? Something to consider if you house rule in favour of allowing the tiny creature to become invisible.
I think the official ruling would be that the tiny creature wouldn't be invisible. It states that the spell affects one creature or one object that weighs one hundred pounds or less.
It's magic. It affects everything and everybody you're carrying at the time of casting, nothing you cannot envelop afterward, and nothing you put down.
You could shoot from inside an invisible tent. The tent stays invisible, you stay invisible inside it, anybody nearby gets a roll to see your arrow slit.
Invisibility is not a lice/tick/Xill egg detector. You can't 'not open' the trapped box by invisibility-ing the lid. You Would make the whole box and contents invisible to outside observers. Shroedinger's cat in a box made invisible after the cat was put in, cannot see outside the box, nothing has changed for him.
All old-school gamer opinion, above.
My halfling caster uses Reduce Person all the time. I'm pondering the acquisition of an intelligent item that has the power to use Unseen Servant 3/day. The item can direct the servant to pick up the halfling and carry him around. That's two 15 ft moves per round, leaving my halfling free to use a full-round action or a standard & move.
He's also pondering getting a kelly green outfit, a pair of fake wings, and a hat of disguise to pretend to be a fairy, "hovering" 3-5 ft off the ground.
And Permanent Reduce Person is a pretty cheap investment, too!
To relate this to your post, I would not expect my tiny halfling to become invisible when carried by the unseen servant.