Can I ask someone out on a date if I have a partner, and a child? If so, how?

Theoretically I am in an open relationship, but neither of us has ever walked through that open door, as far as I know. Part of my problem is I cant find a way to ask someone on a date—if I tell them the truth, then they either think of me as only a friend, or as a disgusting cheater/swinger. And I dont want to be a swinger, and all that it entails. If I dont tell them my full situation, than I am being dishonest, which I cannot condone. I love my partner and do not want another one, I just want new experiences.