Justice of the peace & then big reception?

I have not, but we were going to elope with just our immediate family. Then one of my relatives were going to throw an open-house kind of reception. I still love the idea, and it takes a lot of pressure off costs and planning.

My friend did this. JOP ceremony with immediate family and big reception the next day. I can ask her some logistics if you have any specific questions. It worked out well for them and their situation. Whatever you do, make sure the actual ceremony is as small as it can possibly be so it doesn't look like you're having a tiered wedding!

Is there a reason why? The reception is the expensive part of a wedding.

Yes. We eloped and only had our 2 best friends (who would've been MOH and BM) as our witnesses. My only regret is not wearing my dress to the courthouse.

ETA: We had a marriage celebration at a local restaurant some months later.