Thanks both!
I think what I'll do is with there being routine weeknight meetups is see if I can rally some other folks I know perhaps in a similar situation to do a "kids lap" at weeknight cross practice.
And build them up to doing a full lap.
When I take them to where I practice and setup, I show them the route and such and just tell them "if you get tired, ride over to the car and sit in our chairs". Whereas in a race, there are spectators everywhere just outside the tape and the tape might not be setup in a way for them to abandon easily in parts of the course and get back to me or the car.
That's my primary concern. Having a kid need to abandon without finishing a lap and needing to navigate a zoo of spectators and tape and not be able to get back.
The older kid? Yeah, I can see it being a poop or get off the pot moment. Either go more often to practice with me and do the junior race OR don't do it. I totally can see that.
The younger one? I may beg the case there. I mean, the "race age" thing is by a month due to birthday timing and he's also always been in the lowest 10th percentile for height his whole life.
FWIW......ripping a lap on good conditions at this place for me is like 6:45. 6:45 is me ripping a workout hot lap even, not multiples in a race. So, given my kids are 4x slower they're pushing ever finishing a lap given the course's length. I doubt they would.