In all honesty, if you are not comfortable going out alone on your horse, then I would say neither of you are ready for an endurance (even limited distance) ride. It's been years since I have ridden endurance but I never found it to be a group activity. I would see a parent and child team ride together but out on the trail I found it to be an activity for the horse/rider team.
Your horse needs to be responsive to what you are asking. You are going to have horses passing you at speed so you need to know that your horse isn't going to flip out and take off.
Seriously, I think you need to give yourself another year to train and condition. Endurance is a competitive sport. But you and your horse need to be ready for it. Even if you think you will just go out there and take it slow on a limited distance, it can still be a danger to yourself and others if you are not ready. And at this point, if you are nervous your horse will pick up on that.
See if you can find a local saddle club in your area. Join Back Country Horseman. Check in with local feed and tack stores to see if they have information about local clubs in the area. Having someone to ride with is a good thing, especially for you right now. I hope you can locate a group that works for you. Wishing you the best and stay safe.