Value bet flop

Hand converted with online PokerStrategy.com hand converter:

Play hand

$0.01/$0.02 No-Limit Hold'em (6 handed)

Known players:
[tg]MP3$0.14:///////;CO$2.06:///////;BU$2.00:///////;SB$2.11:///////;BB (Hero)$4.73:///////;MP2$3.66:///////;[/tg]

Preflop: Hero is BB with A:h, Q:s.
MP2 calls $0.02, MP3 calls $0.02, CO calls $0.02, BU calls $0.02, SB calls $0.01, Hero raises to $0.16, MP2 calls $0.14, MP3 calls $0.12, 3 folds, 2 folds, SB folds.

Flop: ($0.52) A:c, 8:d, 3:s (2 players)
Hero bets $0.25, MP2 folds.

Turn: ($0.77) 9:h (2 players)

River: ($0.77) 7:s (2 players)

Final Pot: $0.77.

Results follow:

Hero shows a pair of aces(Ah Qs).
MP3 shows a straight, jack high(Jd Th).

Hero wins with a pair of aces(Ah Qs).
MP3 wins with a straight, jack high(Jd Th).

MP2: VPIP 85, PFR 28, AF 0.8 (107 hands)

Was it OK to cbet the flop? What would bet the right bet size?