Your question is whether this is the right place for you guys.
Yes, it is. There are people looking for a unicorn (a third partner for a triad, usually female but in your case either would work) and there are people currently in triads.
I think actual triads are less likely for the reasons other people mentioned, but you'll find that people looking for "a third" are way more common than people looking for a partner for just one person (at least it seems way more common to me, I could be wrong I guess).
Either way, I wish you the best of luck and I hope you find a partner or two who will make you happy.
How would you feel about a square that isn't a quad? What I mean is, how would you feel if you met another couple, and each of you dated one person from the couple, but not the same one? Would that still work for you, or would you want everyone to be involved with everyone?