Social life & the opposite sex

Hello, I am hoping to increase my social life. In early years I was not a big social creature, however now I feel I am blooming into a more fuller person. I am married and my situation is being friends with people of the opposite sex namely women. My best guess is I probably shouldn't spend a lot of time with them alone. I was thinking maybe having lunch during a work day or inviting a female friend to hang out with my wife present. My wife isn't very social but does enjoy going out but I don't see why my personal development should suffer because of that. If anything lack of social activities has probably hurt me a little. I am not thinking of just having one female friend out on a regular basis. More what I am doing is building a social map where I interact with people on a regular basis...say keeping up with them once a month, sending them an e-birthday card.I guess what I am asking is for pointers regarding the female friends portion of this I feel she will have a problem with it.