Hi Lynne,
Gosh, what memories - I was in the same boat, my husband touring and crewing while I was chasing toddlers, pregnant/nursing and trying to keep my career on track from home. He had glamour and celebrities, I had spit-up and strained plums down my back... Ah, the good old days! tee hee ;-)
Listen, I don't miss the chaos, but in some ways they were the best days of my life. I had kids the same ages and had the added bonus of being pregnant again by the ages you're talking about. And I know what you mean about the kids missing Dad... it's agonizing from so many angles. Throw in 'potty training in autumn' and it's too much to attempt - especially on your own. I can't tell you how to do it now. I can only tell you from experience to wait, just till spring. Here's what I suggest.
Hot weather potty-training is a breeze, seriously. I tried to train a two of my kids in cool weather -- failed miserably. Spring came and they were each 90% trained within three months, no joke.
The 'naked/half-naked kid' approach worked so fast and so easily for me, with each of my four kids. No diaper = no options & even if your son's peeing on a tree now and then, he's getting the idea to pee with control. That's a good thing. (Honest!) But overall, I think you'll be happy to see how often he uses the toilet or potty chair. Here are strategies that worked for me, while I wrestled with doing it alone:
Use games to entice him to use the regular toilet (see below). Carry a potty chair from room to room the rest of the time. TV shows, handheld games and lollipops all work well for keeping him happy while sitting on the potty chair every hour. (Yes, lollipops are sugar, but moms with only half as many arms as duties need to make concessions. And that's why we have toothbrushes! Lollipops last so long that you're bound to get a little pee-in-the-potty out of it, so it's worth the sacrifice.) Make sure he knows that the idea is to get a little pee in the potty and you're guaranteed results within a few days.
For the real toilet, play games. Target practice: Boys love to pee on things. So make targets! Make ice cubes with food coloring, three different colors. Every time you can take him to the 'big potty', plop a couple of ice cubes in the toilet and let him aim his pee at them. Give points: 5 points for melting the red one, 10 points for melting the green one. If you have ice-cube trays that make shapes, use those too. Toilet-paper shapes do well for sinkability - sink a ship, a shark, etc. Go all out, make a score sheet that hangs on the wall (my son LOVED that) and let him earn prizes. (It works with poo, too, but he has to 'sink' the T.P. ship... 'nuff said. One daughter actually liked to score the "plop" sound - gross, but hey, it worked.) Target practice was my best friend while potty training.
When you do start again, relax. Take a deep breath and go 15, 20 minutes at a time if you have to. Don't let yourself think about how overwhelmed you are, what's ahead or what just happened. Being "present" is your best bet while doing all this solo.
The good news is, you WILL get through, you WILL succeed and when your kids have all turned 5 you will look back on these days as the tempering of your spirit, the forge on which all your future indomitability was created. And believe me, YOU WILL BE INDOMITABLE. The sense of strength and self-reliance you'll get from this process will stay with you forever. I'm 200% better for it and you will be, too. It's no picnic, but it's one heck of a worthwhile adventure.
Meanwhile: Each day, jot down the funniest thing that happened with your kids. Keep your notes in a book or in a box, doesn't matter. It's 2 minutes carved from time you don't have, but make it happen. These notes will form your lifeline when you least expect needing one. Mine still make me laugh.
Best of luck! :-)