You are one lucky soab that your wife is into it and the girlfriend too. Plenty of People come on here and go, "i cheated, i was caught, but i realized i'm actuallu poly so it's ok! How do i get my partner to let me try it" or "my partner cheated & got caught. Now they say it's because they are poly. They want to date other people, and they want me to try. I'm not into that, but i don't want to break up either. What should i do?"
You have been lucky to get past both of those hurdles, plus the additional hurdle of "finding someone to date who is ok with dating a married person".
Even though you started out by cheating, it sounds like you accomplished what many people who start off the "right" way never seem to get - choosing partners who are not only compatible with you, but with each other to whatever degree is "ok".
Do yourselves all a favor and drink plenty of water.