R..
My dad would rent a tank of helium, and fill the living room up with TONS of balloons.(couldn't see the ceiling through them, and a forest of string hanging down) :D :D :D SOOO much fun for us when we woke up! We would go out and play with them while we waited for him to wake up so we could open presents. He was smart... and would hide change in some of them (or rolled up dollar bills) so we would pop them for the money. (Then there were less for him to take care of. lol) We would tie balloons to packages to see how many it would take to get it to float, or tie a BUNCH together and push it out the door to watch it float away (now we realize that this probably wasn't the *best* for the environment... but it sure was fun!) I'm not sure if this would work with 2 babys though... choking hazard and all... unless you could set up a "safe zone" for them...