How well do you know the South West? Moving is more than just a property, it is friends, etc. Have you thought as to how you will be in, say ten years, time? Will you still be able to drive long distances? And manage a house? . Children will then be of an age when they are unlikely to want to give up part of their school holidays to be with you. Perhaps you would be better staying closer to where you know people and think of what would be best for YOU to live in 52 weeks a year. A Bungalow or a flat. Even if you are now storing things for your daughter, she may want them nearer to herself in London and perhaps could use a storage unit, where things would easily accessible.
As has been said, holiday times, roads to the South West are dreadful, with journeys increasing by many hours.
So much better if you can within some sort of easy-to-reach place for your sons and g.children as well as your daughter. You are not there to provide B&B, so think about your own day-to-day living needs first.