I'm doing snail mail invites.. I feel like it's more appropriate for my guests

I think if a lot of people on your guest list are younger and/or fb savvy then that's totally fine! 

I rather receive an invite in the snail mail! But I'm 32 and old school like that :P

That's what I do. The only time I didn't do invited on Facebook was for my wedding. I hate buying invitations. So Facebook is easy cause everyone has one but my grandparents

If you want to make it a little mor formal, but still save money, e-vites are a great option. Look into paperlesspost.com and evite.com. Note this really only works if your guests are tech savvy and check their emails. Otherwise, just stick with some simple invitations from target or something. 

I probably plan on doing fb invites for the majority of my guests. Then I'll call or send something to those who aren't on social media. That's how we did our gender reveal party, it worked well.