Hi,
I'm actually here on Freelancer for voice over work but your ad caught my attention.
I work in a materials engineering field and as a sailor, I have a lot of experience using GPS systems.
I don't have kids but two of my co workers have kids that may fall in your target range. One has a preschool boy and the other has 10 yo twins, a boy & a girl. I'm sure that they'd both be up for trying out something like this.
As far as the customer service portion is concerned, I'd need to know more about your requirements.
Thanks,
Karl