I did not stay here, but Candi Dasa is supposed to be a lovely beach town.
We stayed in Ubud and everything is accessible. I didn't find the beaches to be a big deal--they are not tropical; typically tres gritty/rocky. We stayed at Royal Pita MAha (way up the river gorge--very upscale) Drivers w/cars are $40/day, so you can spend a beach day, see the hills/rice paddies anotehr day. The farthest reaches are palces like Amed (not for first-timers unless you have lots of time) but I would happily go back to stay at poincianaresortbali.com--it would have been a better choice than Amed for us (remote small village area)
We went to Benoa Novotel and if you cna get suite/villa at a price, it's a nice beach area south of airport and major temples. Don't miss the Balinese culture/dance rpograms--fascinatiing!!
Loved Ibu Oka pig restaurant in Ubud--very famous hole in the wall--pork to die for!!
Do not miss massage/spa day--if you have to duct tape the kids and go alone, go--it's the best bang for your buck! Thye may like it too--it's so cheap for a whole family at some of the small places
Elephant park would prob interest kids--whitewater rafting, too. Drivers can give you volcano/mt tour or bike tours. BARGAIN for drivers and such but obviously don't cheat them--they are such a lovely charming people. Watch your exchange--I recommend ATMs for most $$ needs. ASk more as needed.