In case useful to anyone else weighing timing of a family UK trip and potential stops on it…
My family (me, husband, 18 yo and 15 yo) headed to London, Isle of Skye and Edinburgh over spring break (very late March & first week of April). We were torn between going then vs in mid to late July and picked spring break for reasons unique to our schedule.
It DID rain a lot. :) That said most rain was heavy misting type or strong drizzle not downpour rain. So for the most part being out and about in it with raincoats was just fine. I think the spring timing worked out fine for the cities but not so well for Isle of Skye.
London: We did changing of the Guard, Tower of London (teens liked), Borough Market (oldest liked), Churchill’s War Rooms (not sure either loved it but they both voted to come see it and neither complained), Warner Brothers Harry Potter studio (the liked it of course), shopping in Covent Garden and afternoon tea. Then each got to do their hobby (climbing and swimming) at a spot in the city - they seemed to like that.
Edinburgh: Did the Arthur’s seat hike (they seemed to like the rocky / dangerous top up at the lookout), Castle (not as big a hit - both liked Tower of London more), and Royal Mile shopping. I think this city’s charms are more for adults than kids/teens. I thought it was beautiful and charming but I’m not sure it resonated as much with the teens.
Isle of Skye: I’ll say that it was a nice time and one teen said it was his favorite part BUT I would not recommend others go in early to mid spring. SO much was brown still vs the bright greens you see in summer. Old Mann of Storr hike was so fogged in you couldn’t see the view at all. A bit better at the Quiraing and both liked that - very cool landscape and younger one really liked hiking around its rocky areas off path. We did a visit to a sheep farmer to see how he used his dogs to corral them and both teens liked that a lot. Neist Point I think was a popular stop too - they liked exploring the lighthouse grounds and going down to the rocky beach area. We also just relaxed some at the AirBNB. The Isle was indeed very pretty but not very vibrant at that time of year and of course very cold. All that said, I’m not sure the 6 hour drive all the way out there was the best time investment on a short trip particularly in spring. In summer it may be different due to being able to enjoy being outside differently and some of the adventure options that open up then in good weather.