Hey Skyler, I've got a similar situation. We're only having about 35-40 people at the ceremony, but plan to have a much larger reception/dance later in the evening. It's a second marriage for both of us so just family to the ceremony. So now I'm trying to figure out how to word the invites for just the "party".
My first thought is that I should do just as you suggested, use the same invitation, but change the wording on it. Afterall, you don't want the ones just invited to the reception to feel like the "B" list by not sending a nice invitation to them too. IMHO anyway...
Hope we see lots of other ideas here though!