Hey RapmasterD, I'm so glad to see you're enjoying your retirement!
The elastic waist trousers are a must. Gatorade is good, but don't drink the RED stuff. Gelatin is good, but again, no RED. Best tip that I haven't seen yet is GummiBears. Yep, they're allowed as long as you avoid the - wait for it...RED ones. Tomorrow morning, you won't believe how delicious a breakfast of coffee and GummiBears is going to be.
Proximity to bathroom is good, chair in bathroom not so much. You won't want to be in there any more than is absolutely necessary, as it won't smell like roses. If your plumbing is the least bit balky, find the plunger now and keep it nearby. This is also an excellent time NOT to use baby wipes. They are NOT flushable, despite the manufacturer's claims, and magnify your chances of plumbing woes. Soft TP is worth its weight in gold. Since you have a kid and have dealt with diapers (hence less squeamish), I can also recommend warm, damp washcloths for their soothing comfort.
The advice to start early is excellent. If you do, you will probably be so cleaned out by the time you head for your procedure, you won't need a towel.
Note to any and all: They gave me pills to take, not slime to drink. I can't tell you what a difference it made. Too late for our friend RD, but keep this in mind when it's your turn. If they don't offer, ask for it. Even if it costs more, it's worth every penny.
3/19/2019 UPDATE: I'm going to pass this link along to another forumite, so I wanted to add that for my second colonoscopy, they gave me the slime. Apparently the pills have fallen out of favor. Much to my surprise, it wasn't especially slimy, and the lemon flavoring packet helped a lot. Also, the things you can eat list has been expanded to include pastel colors of gummy bears (gummy anything, really). Just stay away from the dark colors, especially reds and deep oranges. If you have a Sprouts near you, try theirs. They're made my Albanese and they are addictively delicious. Gummies really help with the desire to chew something during the fasting period.