[SH] NL50 KK 3bet pot river

Prima, $0.25/$0.50 No Limit Hold'em Cash, 5 Players

BTN: $47.98 (96 bb)
Hero (SB): $65.20 (130.4 bb)
BB: $54.69 (109.4 bb)
MP: $71.84 (143.7 bb)
CO: $41.09 (82.2 bb)

Preflop: Hero is SB with K K
MP folds, CO raises to $1.50, BTN folds, Hero raises to $5, BB folds, CO calls $3.50

Flop: ($10.50) 9 7 9 (2 players)
Hero bets $5, CO calls $5

Turn: ($20.50) 6 (2 players)
Hero bets $10, CO calls $10

River: ($40.50) 5 (2 players)
Hero ??? (21.09$ left)

Anon table.

CO played 40/24 after 90 hands, AFq 16, wtsd 26 so far.

Is it a valuepush vs a passive fish? He could still call with TT/JJ...
Otherwise, would be a better plan to cbet bigger, and shove turn vs his stack? I wanted to give PPs the chance to calldown...