Very early in session, and no reads.

PokerStars Pot-Limit Hold'em, $0.25 BB (9 handed) - Poker-Stars Converter Tool from FlopTurnRiver.com

CO ($22.45)
Button ($27.10)
SB ($26.95)
BB ($25.35)
UTG ($40.30)
UTG+1 ($14.95)
MP1 ($55.50)
MP2 ($4.65)
Hero (MP3) ($26.15)

Preflop: Hero is MP3 with A, A
4 folds, Hero bets $0.75, 1 fold, Button calls $0.75, 1 fold, BB calls $0.50

Flop: ($2.35) 6, 9, 5 (3 players)
BB checks, Hero bets $2, Button raises to $7, 1 fold, Hero raises to $23.25, Button raises to $26.35 (All-In), Hero calls $2.15 (All-In)

Turn: ($53.15) K (2 players, 2 all-in)

River: ($53.15) A (2 players, 2 all-in)

Total pot: $53.15 | Rake: $2.65

The likelihood he's raising the flop with a FD is low imo, so his range is mostly PPs (overs and sets), combo draws (very few) or a spazzed out TPTK.

In general, I'm not really happy stacking off on this flop. Is call flop, re-eval turn (shoving this one) a better line?