Not Getting Run Over

Usually, I would consider folding pocket 9's to a big re-raise (the book says KK/AA). But, at this level, on this site I read a weak A, and a strong A. Besides feeling that I had the best hand, and that the SB was trying to push me out, I hoped my pair would hold up with only 2 A's left in the deck (I felt this was confirmed when SB did not insta-call my all-in).

CakePoker No-Limit Hold'em, $0.20 BB (6 handed) - Poker-Stars Converter Tool from FlopTurnRiver.com

CO ($20.40)
Button (Hero) ($12.50)
SB ($48.32)
BB ($11.35)
UTG ($34)
MP ($5.35)

Preflop:

UTG calls $0.20, MP bets $0.90, 1 fold,
Button (Hero) raises to $3
SB raises to $9.40, 2 folds
MP calls $4.45 (All-In)
Button (Hero) raises to $12.50 (All-In)
SB calls $3.10

Flop: ($30.75) J, 10, 7 (3 players, 2 all-in)
Turn: ($30.75) 2 (3 players, 2 all-in)
River: ($30.75) 7 (3 players, 2 all-in)
Total pot: $30.75 | Rake: $1.50

Results:
Button (Hero) had 9, 9 (two pair, nines and sevens).
SB mucked A, K (one pair, sevens).
MP mucked A, 4 (one pair, sevens).
Outcome: Button won $29.25