For me personally I much prefer that my kids and I get lots and lots of vitamin D and then play in the shade when we've had enough sun vs slathering on sunscreen lading with all sorts of chemicals and unpronounceable ingredients and letting it bake on our skin in the sun. That being said, I do use it when we are places where shade is limited like at the beach or when the UV rays are particularly strong but it's really only a handful of times per summer.
For my dckids I generally ask the parents what their preference is whether always sunscreen, sunscreen only when necessary or rarely sunscreen and I go from there. This year I have a group of parents who are sunscreen lovers and that's ok. I prefer to supply the sunscreen since I don't find it to be a huge cost and it makes application so much easier. I start applying it when it gets warm enough that we are in short sleeves.
I honestly don't ever see myself applying it year round. Total waste IMO.