Invites - 100 or 125? What do you think?

I have to order my invites this week (AAAHHH) and my guest list indicates that I have to send out 80 invites, but I'm thinking there may be a few I have to send out to family that live in DR who are not coming - maybe 5-10 more?

That said, should I order the 100 or go up to 125 just in case. I'd hate to spend the extra money and not have any use for the extra invites.

Another question, if I stick to the 100, I'll need extra envelopes, correct? I'm planning on printing them myself.

10 extra, 20?

THANKS!!!!!!!!!