SHould I tell him I'd really prefer a quad, and risk ruining the friendship? If i bring it up, or just drop the dating idea entirely with him, im afraid we'll loose a new and important friendship (our first poly couple friends).
You and DH could also talk privately about how to handle the situation where one of you wants to date one of them but the other doesn't. Does that nix the whole thing? Sort that out. Could do that FIRST -- before talking to the couple in question.
Next? You and your DH could talk to the potentials about the choices on the table:
1) You both could tell the husband and the wife that you would like to date him while your husband dates the wife. (This is your 1st choice preference. Romance + friendship with them.)
2) You could also tell the couple you also are willing for one of you to date one of them. You just date the husband. Or DH just dates the wife. (Don't offer this if you don't have it sorted between you and DH first. Don't put either of you on the spot.)
3) You both could tell them that if the dating preference do not line up at all for anyone, you both would like to be continue to be friends because you both value their friendship and it is important to each of you.
4) You make them aware you also have another BF, not just a DH.
You both could ask them if they are willing to date this way and what THEIR preferences are, and ask them if they will go home to think on it and let you guys know in a week.
Then that gives them a face-saving chance to talk to each other in private and sort themselves out. And it gives you guys a chance to observe how they handle that.
If they get nutter, maybe you both change your mind about dating either or both of them. Maybe you put them on your "Messy people to date" list. Maybe you change your mind about being friends too. Who knows?
But maybe it all works out in the end. You can't know without playing ball. You want to know things. So ASK. Could decide to play ball.
That's the dating time is FOR -- to get to know people better. Some turn out to be a runner, some are not.
You could risk being honest about what you want and ask.