99, draw heavy board

[maxpowers21]

20-40 CAZ

UTG: is thinking aggresive player, plays slightly too loose pf though.
MP: No read

UTG calls, MP calls, folded to me in the BB with 99.

I raise, both players call.

Flop: 8c7d4c

I bet, UTG raises, MP cc, I call with plan to donk turn.

Turn: 6s

I bet, UTG raises, MP 3bets, I call, UTG folds.

River: 5h

I bet.

Should I 3-bet the flop for value, or wait till the turn to try and protect my hand. Thoughts?