Was this collusion and what should I have done about it?

[Abagadro]

Playing 4-8 at the Bellagio this Sunday. I only get down to Vegas a couple times a year so I am a bit out of my element/comfort zone as far as rooms go or I may have acted differently.

There is a father and son in seats 9 & 10 of a game. They are putting on a act of being really clueless and stupid. The father acts like he never knows how much the bet is, when it is his turn, etc. Yet, he is doing things like limp/reraising rockets and checkraising the hell of out people which I woulnd't usually associate with 'clueless' players. They are almost always in a hand together and raise a fair amount.

The hand is question the hand itself is not critical and action is pretty standard with a generally raggy flop until the river when it is just the three of us (started out 7 handed to the flop). It is a J and the father (who started in the SB) checks like he has been doing the entire hand, the son bets. He has been bluffing a bit so I call thinking I am likely beat but the pot is decent so it is worth the one bet as there is a chance I am still ahead. The father has shown no aggression whatsoever during the hand. He then raises, the son three-bets. I fold and the father says "just the two of us? I fold" and mucks his cards. I'm a bit stunned and exchange looks with another decent player at the table and he seems to think that is BS as well.

I rack up and leave without looking at the cards dealt to me in the next hand.

Questions: Was this collusion? Should I have done something other than just get out of the game? Did I overreact?

Also any comments on my thinking/actions on the river with action still to go is appreciated.

Thanks for the replies.