"Bounce back" is the now-obsolete term for upgrading the 1 day/1 park tickets to the 2 day/2 park and 3 day/3 park tickets. It still only allows you a single park on any one day.
You can get a UPH for them (assuming they are staying with you on site) for the 3 days but since it would have to be done at the resort it would run you $187.46 each. For the extra $28, I would personally go for the 4 day PH which can be had for $215 with advance purchase. The extra day's admission for $28 that never expires is mighty hard to resist.
If you have the time before your trip, you can call Alamo and see if you can still get the 3 day PHPs through them for $178.93. 800-225-2475