When you have muscle pain you can adjust like this...
Sore to touch: rest
Sore: higher reps, lighter
No soreness: usual thing
Kids move around on your back. It can twist you out and puts force in funny directions. I like the one where you hold their legs and do overhead tricep extensions with them. Also the human jungle gym is great, hold your arms out straight and spread your legs. See if the kids can make it all the way around.
Just watch your back with twisting.