I seriously question your expertise in things Bali. Ubud is a great base for all sorts of things, most of which are reachable within an hour and fun for this age group. These aren't little kids--they will be well old enough to find artwork and cultural things that are fascinating as well as the more active pursuits. Kuta? Seriously? Besides being an unsafe swimming beach for much of the time due to rips and currents (not surprisingly, it's a better surfing beach), Kuta town nearby is well....not the side of Bali I'd want to be taking my impressionable teen to.

I do agree with you that Bali is honestly a lot longer of a trip than San Diego.