I'm going out to a park with my older horse with a group. I have not done this in years and never very far away from my farm. Aside from tack, water bucket, hay, fly spray, water bottle and bug spray for me is there anything I should be taking that I haven't thought of. We are only going to be out there for a long morning.
Honestly, I wouldn't bother with the hay (unless it's a long trailer trip and you want to fill a haynet for the ride), though water (considering the heat lately) is a good idea if there are no streams for the horse to drink from.
I'd also bring some baling twine, actually. I can think of at least three different trail riding occasions where it came in handy that I know about. Twice when a chicago screw came off a headstall and once when a saddlebag strap broke.
Also: helmet! (not only is it a safety thing, it makes ducking under trees and keeping leaves out of your eyes easier, LOL)
Depending on how brushy the trails you're going on are, it might be useful to wear some kind of chaps or half chaps. I've wished I was wearing my half chaps at least once when I forgot them and we had to pass by some thorny branches.
I always carry a buck knife. There have been so many instances where I have had to use it. One for instance, my horse stepped on a fallen, rotten tree. Her foot went in the log and would not come out. We tried every maneuver to dislodge her hoof. We had to painstakingly cut it off (the log of course), piece by piece. Took about an hour and she was thankfully very patient. Oh and I always forget a camera.
Water for you. You can get a water baottle in a carrier at Walmart for around $5Fill it about 2/3 with water, pop it in the freezer. Top it off with cold water before you head out. You should have cold water to drink for an hour or so depending on the weather.
if your horse is not used to going out with a bunch of other horses you might want to bit him up a tad. I made the mistake of riding my gelding out for the first time with a big group in a snaffle. No brakes. The other horses were for the most part very speedy gaited horses with iron shoes. My gelding (barefoot all around) is a not very strongly gaited walker and we trot-trot-trotted over gravel roads for hours until the OTHER horses were tired and we were invited to take the lead to see if that was what was bothering him. It was, and he glided along in his best running walk ever leading the parade. My aching butt and calves would've been a lot happier if I had taken a shanked bit with me....not to mention that I felt the next day like I'd been waterskiing from trying to slow him down.