Should I have bet a little more here on the river...? I hate throwing away won money, but this guy was SO passive I thought maybe he had A6 or AJ, and was gonna raise me on the river... Was this a good play..?

PokerStars No-Limit Hold'em, $1.00 BB (9 handed)

CO ($54.25)
Button ($107.40)
SB ($14.10)
BB ($66.60)
UTG ($102.90)
Hero ($85.20)
MP1 ($34.70)
MP2 ($35.35)
MP3 ($136.50)

Preflop: Hero is UTG+1 with , .
1 fold, Hero calls $1, 4 folds, Button calls $1, SB completes, BB checks.

Flop: ($4) , , (4 players)
SB checks, BB checks, Hero bets $3, Button calls $3, SB folds, BB folds.

Turn: ($10) (2 players)
Hero bets $8, Button calls $8.

River: ($26) (2 players)
Hero bets $10, Button calls $10.

Final Pot: $46

Results in white below:
Hero has As Ks (three of a kind, aces).
Button has Ah 8h (three of a kind, aces).
Outcome: Hero wins $46.

$10 into a $26 pot on the river is a great value bet, it is too large to raise with out a monster for a passive player, and he might not even raise A6/66 here if he is passive. I mean short of pushing with trips there isn't a better bet, and I don't like pushing into a tight passive with out the locked up nuts. Value betting is better as they are unlikely to do something screwy like push with their trips making a tougher choice for you.