I think you've asked a really good question, and a a pertinent one for many. I am in the situation you've described. I've been married for 13 years and we have two young kids. The marriage has been 'on the rocks' for over 5 years. It started having problems three years into it, and nothing was ever resolved.

A couple of years ago, I re-discovered my submissive leanings. I suspect they're a great deal stronger than I've allowed myself to believe, but I've been unable to really explore them safely. I convinced my husband to try some D/s play in the bedroom. It was fun, to a degree, while it lasted, but it left me feeling like there was so much more to it. Unfortunately, because of the nature of our marital problems, I could never submit to my husband emotionally. After 15 years together, he has really very little idea of 'the real me' which makes it impossible for me to trust him emotionally.

I realize this answer is becoming long-winded, but I really just wanted to speak to your 'Is it appropriate?' question. I don't know the answer. I wish I did. I do know that I am, for the most part, a happy and successful person. But then there's this strong need of mine to find someone I can respect and submit to.