We have friends who have offered the use of their cottage in Cornwall (Polmorla, Wadbridge). This is my kids' (15, 18, 21) first time to England and possibly their only time. Since we only have 10 days I'm wondering if going to Cornwall will take up too much time. I want to do London and some of the other popular highlights not too far from London. (I will add that we will be staying with our friends at their home near Surrey for part of our trip.) Any opinions would be appreciated.
Whatever you do, don't miss the opportunity to visit Cornwall, especially as you have free lodging. Even if you only stay for 2 - 3 days.
Cornwall is lovely. Very scenic and lots of history and lovely food. It is a long drive to get there though (and the traffic can be hellish in summer. I used to live in the west country and the tourist traffic to and from Devon and Cornwall was the bane of our lives). I think it really depends on what sort of things you are into and what there is to do in that particular area. Although I think it's a lovely county I would probably skip it if I only had 10 days and there were other things I wanted to do. It really depends on what sort of things you like seeing and doing.
Cornwall is a very romantic part of England, full of ruined castles, Arthurian legend, megalithic stones, tiny rugged coves, literary associations, moody moors, and tiny back roads. Is that what appeals to you about England? If so, then don't miss it. If not, it is a long drive.
If you will also have the loan of your friend's car, consider using the train to get to Cornwall. Let your kids read up on the Merlin and Arthur stories (check out the "Crystal Cave" series and others). Then decide. Here is a link to an article I wrote about day trips out of London: http://www.aaacarolinas.com/Magazine/2008/Jan-Feb/britain.htm?zip=28201&stateprov=nc&city=charlotte
Fell free to private message me- we have been to the UK more than 40 times and took our kids several times when they were the ages of yours.