Traveling with 9 month olds

twinmommy-2

We've never traveled with our twins before and plan to visit family when they are 9 months old. It would be a 15 hour drive by car, so we think it would be best to fly. (3 hour flight)

I would appreciate any advice about flying with twins and staying in a hotel.   
Is there anything I should pack besides the usual diaper bag stuff? Where should they sleep in the hotel room? The only thing I could think of is an inflatable pool  lol
We don't have a pack n play.

Thank you!