Telling your spouse/potential spouse from the very beginning is very important. Let me explain. I've been married twice. The first I didn't say anything until we were on our honeymoon. It was a disaster! She hoped I would get rid of the idea. Instead I kept it secret - unfortunately, unsuccessfully It broke us apart, she felt I was holding out on her in our relationship. It's what caused the end of our marriage after 15 yrs.
The 2nd marriage, before we were ever married I shared with her before I even asked to marry her. This marriage, on that aspect was much better, more open. I didn't have to hide it. Our sexuality was very enjoyable. But what broke it apart is I didn't take into consideration of how incompatible we were in other parts of our life.
So my opinion is Share, but after you share make sure that the relationship will be compatible in all areas. Assure you can be comfortable with the person in all that you would do together. Don't be satisfied that you have someone feeling alright with you in diapers or even diapering you. The marriage will not be based on those reasons to marry. It's how you really love the person, can get along with her.