1) Outside alone is a no-go at just about any campground. If the owner finds out (and people will likely notify them), you are likely to be asked to leave.
2) Inside, you need the air/con running as campers tend to heat up well beyond the outside temp. On an 80F day, the interior could be well above 100F (even with the windows open).
3) Even inside, if he barks, expect to be asked to keep him under control or be asked to leave. Keep in mind, he will be hearing lots of new sounds as he is in an unfamiliar location and that could trigger him to bark.
PS: You were vague on the breed. I'm not sure if that was intentional or not but if he looks like a pit bull, doberman, german shepard, or other "aggressive" breed expect some parks to not allow him. It doesn't matter how sweet or well trained he is. It's mostly an insurance thing, so no point getting mad at the owner.