value-betting my kicker

Both villains are straightforward and will call to the river a) with any piece of the flop, b) to keep me honest, c) if their nose is itchy. VPIP ~50-60 when it's been 4-5 handed. SB is slightly more tricky and more fishy to boot.

.5/1 Pokerroom (3 handed)
Pre-flop: I have A[img]/images/graemlins/club.gif[/img]4[img]/images/graemlins/club.gif[/img]
Hero raises, SB calls, BB calls.
Flop: (6SB) 8[img]/images/graemlins/spade.gif[/img]8[img]/images/graemlins/heart.gif[/img]8[img]/images/graemlins/diamond.gif[/img]
SB checks, BB checks, Hero bets, SB calls, BB calls.
Turn: (4.5BB) 5[img]/images/graemlins/diamond.gif[/img]
SB checks, BB checks, Hero bets, SB calls, BB calls.
River: (7.5BB) 10[img]/images/graemlins/diamond.gif[/img]
SB checks, BB checks, Hero??

Throw in one more? Check it down?