Electrical Question

I would not upgrade the main breaker unless you know for sure what gauge wiring is feeding it.

If you keep all the branch breakers the same amperage, it's possible but you need to upgrade from the pedestal to the box. For example: if one branch is currently 20amp and you keep the 20amp breaker on it, in theory it should be fine. If you want more amperage on a branch, that branch needs to be reviewed and likely upgraded.

40amp makes little sense as no campground has 40amp pedestal outlets,  you can't draw more anyway. The only difference is it will largely guarantee the pedestal breaker pops before the main trailer breaker on a 30amp outlet.

50amp is a different ball game: 30amp @ 120v is the basic and 50amp is technically 50amp @240v but in practice is 2 - 50amp @ 120v legs. If done right, it could offer some minor benefits (ie: run the air/con, hot water heater & microwave simultaneously) but you have to do it right and probably need a whole new electric panel.

Since you ask this question, I'm going to guess your experience level is such that you want an electrician to set it up and install if you proceed.

Wire size dictates breaker size.  #12 wire on a 20A, #10 wire on 30A.