I've traveled with an air mattress before, and it worked quite well. I have a queen-sized Aerobed (similar to this one: http://www.aerobed.com/Premier-Air-B...-P1954C40.aspx).

I was visiting a friend and using it in his apartment, not in a hotel. Granted, the air mattress isn't necessarily "light-weight" and almost filled an entire medium-sized suitcase, but since I have a baggage allowance with my preferred airline, it wasn't a big deal for me. I packed the mattress, some sheets, and my clothes into one suitcase...enjoyed a few nights of very comfortable sleep, then sent everything back home.

The Aerobed I have is double-cushioned, which makes it heavier. Since you're kids are probably are more resilient than my broken body, you could probably get away with just single-cushion mattresses. I've heard good things about Coleman and Aerobed.