I live on a farm, so you'd think I have lots of places to ride, but once the land is seeded and growing a crop, I also struggle with a good place to ride. So I can give you a few tips on how to make riding in a small location a bit more interesting to you and your horse.
I agree that your horse isn't going to be as fit as ideal if you can't ride her at least 3-4 times a week. You may have to accept that she won't be able to work really hard at camp 3 times a day, but she still could be fit enough for some riding and groundwork.
Lunging can be boring. I do my best to keep my horse interested in it by varying the pace and directions as much as possible. You can also set up poles on the ground and even tiny jumps to have your horse lunge over them. Make your lunging creative so your horse has something different to do each time. One day you could trot him over poles set about 4 ft apart, then the next day set up a little jump or two.
If you aren't allowed to ride until your mom's home, perhaps you could ground drive your horse. If you've never ground drove before you should get someone to show you how so you and your horse keep safe. After that you can do almost anything with your horse. Maybe people drive their horse over ramps and other trail equipement, zig zag back and forth between pylons, practice their walk/trot transitions, etc. You don't need expensive equipment, I use two lunge lines for my long reins, and I use my normal saddle and bridle. You can can trot your horse as long as you can trot, so you'll both be getting fit!
And lastly, I would agree that your paddock is probably your best place to ride. Trot and lope inside for fitness. For fun you can set up all sorts of obstacles using equipment you already own. Teach your horse how to walk, trot and even lope the barrel pattern, or the pole bending pattern, or the Western riding pattern. Work over trail equipment and tiny jumps. If you have a good imagination you can do almost anything! I use plastic pails, wooden boards and rails and other obstacles to create new things for me and my horse to do.
And lastly, don't forget that leading your horse can improve its fittness as well as your own. I know people who jog regularily while leading their horse. That way they get fit and the horse also gets excercise.
Good luck and have fun at camp.