To reiterate what everyone else says - bet the flop. The main thing is nobody at 25NL sees the hit set so long as you don't just push AI right on the flop. Especially with that many people in the hand and a straight draw (at least) available, you want to value bet there. Personally I like to slam down a bet to see who's willing to play ball - so a value bet - and ramp my bets up afterwards accordingly. You probably coulda pushed on the river and been called since almost all fish cannot lay down 2 pair for their life. A very large amount of my set winnings come from guys who hit 2 random pair and can't lay it down when I go AI. Also, the op's $5 river bet to me at least says he's willing to go AI for this pot. (I know this is easy to say in retrospect though!)