Well, let's see... you have three dyads and there are seven days in a week. You and your gf could see each other twice a week, your wife and her bf could see each other twice a week, and you and wife would have at least three full days together. Make sure at least one of those is to date each other and not just be focused on household and parenting. One of the days you each see your other partners could overlap, too, which would give you more time to be together with family and less time the kid is with a babysitter. Google Calendar is your friend.
There! That wasn't hard.