At 10-12 weeks old, I would wager a small amount that the kittens are still pretty much adaptable to the switch to indoor living. Something that is a more likely possibility is that the kittens, once placed in their new homes, will develop sneezy, goopy, upper respiratory symptoms and possibly diarrhea. It is a frequent occurrance while their little immune systems are adjusting to their new environments and their digestive systems merge with the new food/feeding schedules. Most of the time, they pass through this quickly, and without vet intervention in the form of antibiotics - but if they are sneezing green, (as opposed to clear or yellow), the vet needs to boost them up a bit with some antibiotics. If they aren't blowing green, DON'T give antibiotics as this weakens their own immune response, and may cause problems down the road fighting other normal things. Also, make sure whoever takes your kittens feeds them exactly the same foods as you are feeding and at the same times/amounts. This will aid in preventing the tummy problems somewhat.
You might want to tell the people who take your kittens that they should have their vet see them ASAP. Did you take the litter in at 6 weeks for their first shots and deworming? Your new owners will want to do that if you didn't.
On a humorous but related side note, I adopted a real sweet little boy cat that my neighbors were going to take to the shelter. He had been born in my barn, and so had been an outdoor cat from the get-go. My neighbors adopted him at around 8 weeks old but he was always an outdoor cat to them.
2 years and 4 or 5 trips to the emergency vet hospital later (torn ears, bite wounds, etc.) they were "sick of it" and wanted to be done with him. So, I just started feeding him on my porch. Pretty soon, he stuck around enough for me to catch him and get him to the vet. Well, praises be, he was healthy (I mean, I was SO surprised he didn't have all those nasty diseases that they can get out there!) and we got him neutered along with his vaccinations, Advantage and heartworm meds. This was in the month of August. I tried to bring him into the house, but each time, he would panic, and throw himself into the window glass trying to get out.
By November, the weather had turned colder and Buttons, as he is called, stayed up on my porch most all of the time. I made a place under my wicker loveseat for him with warm blankets and his food/water dishes. One particularly nasty night (thunder, lightning and strong winds), I opened the kitchen door to go out and check on him - well, in like a bullet he shot through that door!! He skidded across my vinyl floor and crashed into the freezer - righted himself and has seldom left the inside of my home since. >grin< At first, he didn't want to use the litter box, so I did let him go out to do that - but he was always right back up on the porch afterwards, begging to come back in.
Best of luck,