You should choose your 3bnai ranges based on the expectation of how the other two options perform, (folding and calling vs a minraise) if it shows better expectation than the other two then that would make it a good candidate to put in your 3bnai bluff range.  You will need a decent sample on your pokertracker to compare results. 3betting any 2 suited cards would mean you are going to be 3betting too much and would be exploitable to players just clicking it back.  First assign a 3bet get it in range, a 3bet range that dominates a flatting range ( like kq vs k10 and qj) but is folding to a 4bet shove and then include some bluffs with a range that does better 3betting than flatting or a range that is just outside the bottom of your calling range.  My preference is too 3bet bluff with small suited connectors because i feel they perform better postflop if called.