Presumably you aren’t the parent of a 5-7 year-old child. I might try this manually and save some money but my kids will absolutely cherish coloring themselves, their friends, and their parents. We’re on vacation now and this is gonna be big when we get back.
Interesting presumption. I know about the 100-page coloring books because I've bought them. Paying $1 per page at the speed they get colored would cause me to go bankrupt. I presume you're fabulously rich, and it doesn't matter.
You may want to give dibulo.com a try. We also launched a photo -> coloring page, but we will go one step further that you can bring it to life again.