Ok, so here's an update:
We have started dating other people. He has a nice girl he is seeing, and I have a couple guys that I am talking to, though I have stronger leanings towards one. Everyone is completely informed of what my husband and I are and what we are doing, and everyone is ok with it. The girl my husband is currently dating will only be a short-term thing, as she will be moving to a diff state in about 4 months or so. Both the men I am talking to are looking for long term, and understand what that would entail.
Now for the rules....they are morphing and changing as we go along. We thought we wouldn't want to know anything about or talk about the people we are seeing, but we have found as long as we don't SHOW each other exactly what the other looks like, we are totally fine with talking about them. There was a little flub-up with communication on my husband's part, but I brought his attention to it immediately, and it hasn't been an issue since.
So far so good!