When using Captivating Poke Puff can I choose to NOT put any Basic Pokemon onto my opponent's bench, or do I have to put at least one down if I'm able to?
No, you don't have to put any Basic Pokemon onto your opponent's bench if you don't want to.
Source: TPCi Rules Team (2016-08-11)

Relevant cards

Note: All applicable cards may not be listed below.
XY11_99