Welcome to our forum.
However you approach the situation at hand, I would avoid fast and loose. Have a sit-down with the three of you, find out what everyone's emotional status is, and find out what everyone's limits and boundaries are. If you plunge in without this information, you could find yourself in the midst of a mess.
Although I don't say avoid this altogether, I do say that successful polyamory requires a lot of communication. Therefore, communicate first; act later.
I hope Polyamory.com can be a continuing source of info and advice for you.
Love means never having to say, "Put down that meat cleaver!"