When I had my latest mole check done I spoke to the dr at the clinic about the kids ones. He said that freckles are a result of sun exposure. Not bad, not good, just a fact. Skin type/colour of course plays a role.
Slowly but surely my boys are getting more and more. They are sunscreened a lot but some sun exposure is a good thing too. Be as careful as you can with their skin, but accept that it is inevitable.
I just hope that what I know now is going to benefit them later - and they'll have a few less freckles than me.