I think it’s important to make clear to the person you are dating that you aren’t looking for any help with parenting. That’s your territory, especially in the early days. I had a boyfriend once who wanted to get way too involved too quickly, and my child just doesn’t need the potential disruption that would cause.
For this reason, I wouldn’t introduce the person I am dating to my son as my ‘boyfriend’. That said, it’s easier said than done to keep them totally apart, and often just not practical. My personal solution here is to ask my boyfriends to work by the rules of a public swimming pool: if you wouldn’t get away with it there, don’t do it in front of my son. For me, this means no sleepovers. But it also means more special time as a couple when you do manage to escape for those precious nights away (once you’ve found a very trusted babysitter, of course).