u/BigStalos

Hi 3 friends and I are planning on visiting the park for about 3 days in September.
I saw that for now there are still a few spots available in the government website.
I have a few questions.
Do we have to order the spots now? Will they disappear quickly?
How crowded it is in September? Will there be massive lines in the entrance?
Are there decent campgrounds outside the park but not far?