J.-
Personally, I feel that it's up to you as to what YOU want, but being the youngest of 2 daughters in my family, I can tell you how I see it from my point of view. My sister and I have nearly 6 years between us. We played together a little bit when we were younger, but we fought a lot and as we grew up, she kind of became like a second mother to me, but not in a way that I liked. Anyway, the age gap between us caused a lot of friction because she was always like 4 stages ahead of me in life, and our interests were never the same. To be honest, and I know she would say the same, we didn't even really like each other for many many years. It wasn't until we were both adults, in the sense that we were both in our twenties, that we started to develop a relationship. We are the best of friends now, but those years growing up were tough, and I found myself resentful of her, just as she was resentful of me.
In my opinion, I feel it is too big of an age gap, especially 10 years. However, in the end, it is really up to you. I just wanted you to know what if was like from a "daughter's" point of view. Good luck with your decision.
A.