Are your teens interested in the Loire? Visiting all the chateaux? My kids would not have been interested.

Thank you for the help and suggestions.
janisj - I know Stratford-upon-Avon is on her list. Not sure which others. A good idea to stay a couple days outside of London. We'll certainly look into that.
dreamon -Hadn't thought about cycling, but we checked out kayaking in the Loire. I may take a look at cycling as well.
HappyTrvlr - Yes, thanks, my girls are interested in the chateaux.
BDKR - thanks. Looks right up my alley.

We took our kids to Europe as teenagers. We camped and didn't do much in depth visiting.You might want to take the ferry to le Havre and see Etretat and Honfleur. Rouen is a good place to visit with Jean of Arc's history, plus the Monet light show on the cathedral.

I would consider Mont St Michel for sure. The Beauval zoo near Saint Aignan is wonderful and a change from castles. Amboise is interesting for Leonardo Da Vinci museum. I would let your children pick some places to visit. Happy planning!