Sounds like a great idea.
I'd go to the local book store and see who is doing what and at what price they are selling it for.
I have no idea where you live, but the bigger the city you are in the easier it will be to target a price.
I'd also do a search on the internet for "Childrens Cookbooks" "Childrens Recipes" "Kids Cookbooks" etc...you get the idea. I am sure they will have prices too.
However don't work backwards.
First write your exciting, entertaining, healthful, encouraging, information packed book of recipes aimed at parents who want their children to eat in a more healthy manner.
Then shop your masterpiece around and a potential publisher will give you a better idea of the target selling price.
Retail pricing has many variables including but not limited to: book size, book format, paper quality, cover art, hard cover, soft cover, your name, your qualifications, initial printing, etc...amongst a whole bunch of other variables.
Don't do it with visions of dollars dancing in your head.
Do it because it is your calling.
Do it because you wake up every morning and it consumes you!
Build it and they will come!
Success will follow your desire
Good luck and I mean it sincerely.