I finished my 2nd Appleseed last month. I'm scoring consistently in the Sharpshooter range, and I missed the Rifleman score by 1 shot twice during the qualifications in the last event. The rifle and personal prep FAQ's are here:
https://appleseedinfo.org/how-to-prepare/
They have printable checklists which make it easy to follow and pack. For both ranges I attended, we were on covered concrete, not gravel. I wouldn't want to be on gravel all day even with the high end shooting mat.
The one other recommendation I will add is one should definitely have elbow and knee pads, as this make a huge difference. On my first event I didn't, and my support elbow was bloody at the end. I only did one day that time. I also wasn't as fit as thought, and increased my workout routine before attending the second one. The second event was great, I wasn't as sore, was better prepared, and I attended both days.
There were quite a few kids at both of the events I attended, and I'd like to get my niece & nephew into this once they're a bit older. I think this is an excellent event every kid should attend.
Don't give up Spats, get the gear together and practice, and I'm sure you'll like the next one. I would choose a different location though, and look on-line to check the facilities of the range first.