$50 PLO on UB, as usual. I have a full stack.

I have [Kh][Qc][Ah] in the CO and raise pot. Button calls (he has full stack as well), BB comes along (he has around $20), and MP calls.

Flop (4 players, pot=$10): [Tc][4h]. BB bets $1, MP calls, I pot it, not just for a variety of EV-related reasons but also because I can't stand it when they make these bets). I can't really put them on a hand, but I'm slightly worried about the nut flush being out there or some of my outs being gone. At any rate, button calls and BB pushes in his last few bucks.

Turn (3 players, pot=$60, one player is allin): . I push in (effectively $25 to call).

Any thoughts? My main reason was that it was likely that the button was still drawing, and that I shouldn't give a free card. Also, if I check I'm probably should call a bet, so I might just as well keep the momentum (I know, vague reasoning, but it seems to apply here). Also, I might get button to fold the nut flush draw. Finally, I may or may not want to create a side pot here?

Yup, I like the line for every reason you stated. If someone had a set then you cross your fingers and hope it was the BB so you can take a side pot. You still have 2 possible outs towards the holy grail as well.