RV Park near Yellowstone

Thanks Bigdogger! Yes, we would never try to do this without reservations. I just wanted to know if the grant Village stop is a good one or not and if the larger over 40' sites are available for reservation over the phone for our son. I think that's how I read the Xantera website. It just didn't seem real clear and I wondered if anyone with a 40+' set up has been able to make a reservation online as it doesn't seem to be an available option. I guess I will just have to call them and ask them the question....although it's too early to make the reservation for next year and they seem to stumble over that and don't often have the answers I am looking for as it is "too early"! But I am a planner and am trying to get some preliminary info. We often go places without reservations and much of this trip will be like that ( this is a small portion of an 11 week trip)....but not at a place as popular as Yellowstone. We aren't that much of a gambler although I know many people do it successfully.
Thanks for your input!