If you just focussed on Scotland (or Ireland) for the two weeks I feel you would get much more from your trip.

With a few days in Edinburgh, meander up to the Cairngorms, catch the bottom of Loch Ness and then head over to Skye and Mull and then drop down through Glencoe into Glasgow for a few more days you would have the chance to really start to explore Scotland with places you can visit what would be of interest to your children, rather than just do a whistle stop tour of a few places and see it all through the window. I am happy to do a road trip but I draw the limit at 4hrs of driving a day.

A word of warning - March can still be quite wintery up in Scotland. I did the NC500 back in March 2022 and we were exceptionally blessed with the best March weather for decades but if it's a cold spring then you can still encounter the tail end of winter. You also don't have the benefit of very long days in March, less than 12 hrs of light