What is the best river play here? Button is a very weak player. Once he just calls the UTG's push on the river he has announced that he does not have the straight but would like to see a showdown, right? In which case I should make a small raise? A good player might flat call the push with the straight to try to keep me in, but a poor player would likely raise, right?

Poker Stars 100NL 6-Max

Stack sizes:
UTG: $25.90
UTG+1: $216.35
CO: $94.85
Button: $82.55
Pozzo: $98.35
BB: $101.95

Pre-flop: (6 players) Pozzo is SB with
UTG calls, 2 folds, Button calls, Pozzo calls $0.5 (pot was $3.5), BB checks.

Flop: ($4, 4 players)
Pozzo bets $2.5, BB folds, UTG calls, Button calls.

Turn: ($11.5, 3 players)
Pozzo bets $10, UTG calls, Button calls.

River: ($41.5, 3 players)
Pozzo checks, UTG is all-in $12.4, Button calls.

all in

if he called with a gut shot or a backdoor draw and got there, then i guess I just lose some money