Have you thought of a transatlantic cruise ( wonderful relaxation) ending in New York, with a 3 day stay in New York before flying home. QM2?
What kind of things would you consider 'relaxing' - touring/sightseeing with someone else driving ? doing nothing much other than read, sleep, eat,in a place with beautiful scenery? sports activities?
What time of year?

Virgin Holidays Do 4 nights vegas 7 nights mexico and finish with 3 nights in New york.....

we have done SF,Vegas,LA with them,and Orlando,NY and vegas and they have been outstanding holidays not sure if thats what you looking for....

http://www.virginholidays.co.uk/brochures/usa/tours/tours_by_air/las_vegas_mexico_new_york_2009/

We've done a few cruises and looked at the QM2 option but it looks a bit pricey - we're taking the kids and will have to go in July/August 2010.

As for Virgin, I've just obtained their USA brochure and there's some good stuff in there. I quite fancy 3 nights in New York followed by a flight to Florida for a week on the coast. The kids, of course, would prefer Disney. Perhaps the QM2 option will be cheaper after all!

Thinking about it, the Southampton to New York opyion on the QM2, 3/4 nights in New York and a flight back might not be such a bad idea after all. Where should I look to get the best deals on this sort of trip?