Don't throw away your checkbook yet. Every year I seem to stay at a few CGS that do not take plastic - cash or checks only.
I use St Brendan's Isle for my mail in my domicile state of Florida. Periodically, I have them forward my accumulated mail to General Delivery at the local Post Office or to the CG/Resort I'm staying in.
It sounds like you want to do a temporary change, which is different then the permanent change that full-timers do.
If looking for a mail service with the intent of going 'full time', choose your mail provider carefully. There can be tax implications depending on the state you choose as a domicile state, health insurance cost effects, etc. Last - I would not want to change and then need to go through the effort of changing my address for everything (Driver's License, Banking, etc).
Very good advice about changing your bill paying to doing it electronically. I also do all my banking with Alliant Credit Union. All banking with them can be done on-line.