A few points that come to mind reading this thread (as a daughter of someone who has had 12 skin cancers and has volunteered for cancer charities)
*sunblock should not be applied once you're in the sun. It should be applied inside, preferably before you put your clothes on to ensure good coverage i.e. not stopping short of the clothing lines, and given 20 minutes to soak in
*higher factor suncreams are not necessarily better, they just have more chemicals. For this reason I only use factor 25 on my DD with sensitive skin (the lowest I could find for children). Higher factor suncreams are largely a marketing exercise, especially as people think factor 50 is double protection of 25
*My DM was vitamin D deficient. Dr told her to spend 15 mins per day at 6 in the evening with her sleeves rolled up, i.e. face still covered with a hat as it is sensitive skin. Nobody needs to spend an hour in the sun at lunchtime to get their fill of Vitamin D.
*suncream will never outdo the need to stay out of the sun in the middle of the day during summer, it does not block all the rays and it can be rubbed off. Also waterproof suncream is a bit of a joke, it will still come off and when you're in the water with the reflection of the sun, you're much more likely to get burnt. Best to use zinc cream and sunsuits for children
*the majority of skin damage is done before you are 18 so yes it is right to have concern over children getting burnt. One bad sunburn as a toddler or teen could result in a skin cancer in middle age.
*there is no such thing as a healthy tan. Tan is a sign of sun damage just as sunburn is.
OK time to get off my soapbox now.