I am a spouse of a now retired AF officer. I get the juggling kids. I have 3 that are 2 yrs a part in age. I spent many a night running and dropping off kids at different soccer fields and asking other parents if they can watch as I ran to the next field to drop off the next kid, and the same with the last, than running back to the 1st to pick them up, and so on and so forth until I got back to the last. I don't think I saw any game.
The beauty of spouses is they get it!
You state he is 15, when does he turn 16? Have you thought about not doing either right now, but instead get settled into your own routine. During this time, look into the local Y and how to get certified as a lifeguard. This does three things.
1. Keeps his foot in swimming
2. Lifeguarding certification usually occurs later at night (6-8 pm) or on the weekends, allowing you to be able to juggle more
3. Parlay into a summer job, which help him for his application along with keeping up his skills.
~ Your DS does xcountry, but most HS students competing in a fall sport will not train until a few weeks prior to the start of the school yr., thus it should not be a confliction.
~~ Our DS worked full time as a guard starting at 16, he had no license. I would drop him off at 8 a.m. to open the pool and pick him up at 5 pm. 5 days a week during the summer.
I don't know where you are located, but where we live/d, (NC and VA) Varsity swimming was for juniors and above, but that is also because it was competitive from college recruitment aspect. If you made it as a freshmen with them you were going all state.
Again, I don't know the age of your other children, and trust me I get the single Mom, Dad deployed aspect, but if he is an All State competitor level than I am with Humey, pay for an Uber or back away from some of the activities your younger kids are participating in at their current level.
I truly, truly get it as a military spouse. The guilt is amazing. I will give you the happy news. Someday in the near future your children will look back at you in absolute AWE even if you can't juggle it all. If you are fortunate like my kids, they will joke/tease about how you juggled it right in front of you when they hang together. Do you remember when our sister was in horseback riding and you and I were in TKD when Dad was deployed? Those days were great. Mom came home from work at 4 took her to riding lessons, dropped us off at TKD and we would stop at MickeyDs or get Chinese take out for dinner! The siblings reply is usually, yeah, and once Dad came home that all ended! I officially became their favorite parent yrs later after them yelling at me I hate you while he was deployed.