2010 Prius and kids...

Wouldn't be a problem at all. It's not much different width wise than the 2nd gen and 2 fit in them. No one can really sit in the middle between the 2 seats but the seats themselves will fit.

Good luck with the family

 

Yep. Ask efusco, he has 3 kids and 3 car seats in the Gen 2!

 

I have 3 kids as well. In the 2010, we elected to put the infant car seat on the left, despite my wife's objection to safety. In the center, the center console slides back into the base making it almost unusable. My 8 year old doesn't mind the middle as she has better visibility. My 13 year old objected a bit more to the arrangement as she doesn't get her little sissy between her and her other sibling.

If you're using LATCH, the outboard positions are better anyway.

I did put a receiving blanket under the base to protect the leather, and a rolled up towel under one side to help level. Some suggest a pool noodle, which may provide better results.