Is there any American family of 5 that hasn't used an air mattress in a hotel at some point?

Seriously, if you have 3 kids, USA hotels often have 4-person-per-room (usually unenforced) rules, and it sometimes makes no economic sense to book two rooms. When the kids are young, any half-way decent air mattress is fine: you actually don't want the better ones because there's the trade off in size (you want something compact if you're travelling by air).

When the kids become teenagers, this becomes more problematic because nobody over 100 pounds seems to really enjoy sleeping on a "blow up bed."

FWIW, if you need extra bedding, I find the Choice hotel chain to be the most accomodating. Their hotels are obviously not as luxurious as Marriotts, Hyatts, Westins, etc., but they get the job done without having to incur the expense of booking two rooms.

Also, even without extra bedding, if I'm travelling with the family, I try to avoid hotels that have only double beds instead of queens. You generally pay NOTHING more for a hotel with queen beds instead of doubles. Frankly, I'm amazed that any USA hotel would use doubles these days. Americans tend to be large, and we tend to like our beds un-tiny. Doubles are just silly.