Helmets, band aids - when my kids (and their friends who often came along) were little they were amazingly gifted at hitting things, running into each other, falling over, etc.
Pumps - I've had good luck with Topeak floor pumps but when I was pumping up tires on lots of kids bikes each weekend I bought a cheap electric garage tire pump kinda thing - worked great.
Good routes - with our kids I found rides went much better when there were rest stops where there was something for them to play on or explore, vs. just sit around and eat/drink. Back in the 1990s I wrote a book "Family Bicycling in the Washington Baltimore Area" to highlight routes we found that worked well that way. Your town might have a bicycling club that can give you information if you don't know of such routes