Well, first of all, if he's ready before you are he'll just have to take a cold shower and wait. Don't do anything you don't feel okay about. That's the most important thing. If he or anyone else you might be with in the future can't respect that, they're not a person you should be with.
[ As for the rest... well, this is going to be awkward and personal either way, but she'll at least try to skirt around any intimate details. He doesn't need to know about how mommy and daddy got to porking. ]
This probably isn't going to sound very helpful but... you just know when you're ready. Sure, you're probably going to feel nervous and maybe a little scared but you'll know. And, besides, it's not like you have to uh... get right in there on your first time. You do stuff and uh... if that feels right then you do some more stuff until it doesn't feel okay anymore.