100NL AK play-along

[NDHand]

Party Poker No-Limit Hold'em, $ BB (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

Button ($69.41)
Hero ($98.65)
BB ($103.25)
UTG ($35.93)
MP ($49.50)
CO ($62.85)

Preflop: Hero is SB with A, K. Hero posts a blind of $0.50.
UTG calls $1,MP raises to $3, 1 fold, Button calls $3, Hero (poster) raises to $12.5, 1 fold, UTG folds, MP calls $10, Button calls $10.

Flop: ($41) 9, J, 3 (3 players)
Hero ???

I was hoping to fold out MP here and play HU vs Button, who was truly horrible (minbetting 1$ in 25$ pots, calling down with trash, over 60 VPIP, etc). However, our unknown villain, MP, called. I think it's very likely I still have the best hand against Button, but my hand really isnt that favorable against MP's range here. What's the best line here?