Hi! I'm going as a first timer this year as well. Spectator / Camper. I've asked the same question on a different forum and was told that the BEST days to attend are going to be Wed 14th, Thurs 15th, & Friday 16th. The last day of the event is on Saturday the 17th but was told that most people are packing up that day. I will be arriving on Tuesday 13th some time, and leaving Saturday 17th in the morning.
What I'm gathering is that the majority of attendees are going to be scheduling their vacation that week. I figure the average person that lives within a 1000mi. radius with campers / RV's will spend the weekend traveling, enjoy the weekdays there, and leave to travel home the second weekend. I'll have a late start because of Mothers day.
I'll be pulling my camper and will have my Honda Rancher (4Wheeler) loaded up in the pickup bed for personal transportation while there.
I hope some of this is helpful!