I think that most guys as long as they know that you are bi will not want to play with you simply for fear that in the heat of the moment they might find your hand (or something else) touching them and ruin the moment for them. There is a massive amount of homophobia among straight men, and while it may be something innocent if they knew you were straight and you touched during a 3some it would be nothing, but knowing that you are bi there will always be that fear that you are attracted to them and may want more.
I definately agree that you should be honest. There are plenty of couples out there that are looking for bi guys, so you aren't that unwanted. It's just a matter of finding the right couples. I do think you have it easier than most couples who are seeking bi-females
