Could I spend 20 grand in a week at Disney....
Nope.
I would upgrade your hotel from a value to at least a moderate. Also I would rent a car if you don't do so already--the buses are too slow. That would not even come close to $20K. We have stayed at all levels of hotel, and generally just avoid the values now. We only do this to stay away from the big groups. The facilities are fine, (I love Mr. Potato Head at POP) we just don't want to stay next to 1500 screaming teenage......cheerleaders, foot ball player, band member, visitors from Brazil, you can pretty much insert any large group here. It is worth it for us to stay moderate to ensure excellent sleep.
Here is my thing. Disney is a theme-park. Once you pay admission, and airfare to get there, everything else is about customizing to your families experience. Disney's food is ok, not great. We are not huge eaters, nor do we want to do 3 sit down meals (takes up too much time) so all the premium food packages are wasted on us. We live in Chicago and travel a lot--so we have access to great food. Most of the extra experiences, spa, boat rentals, can be done closer to our home on a weekend, while not using up valuable vacation time. We do like the water parks, and visit one nearly every visit (weather depending) and also probably do mini-golf 3 times in a week--those things just aren't $20K expensive.
Disney's best hotel, is nowhere near the best hotel in the world. Husband travels for work, and unless they are assigning you your own human being (not even kidding) it is not even near the top of the standings. Not that their Deluxe resorts are bad, they are just on par with a mid-level Marriott. The Deluxe hotels are only deluxe because of their proximity to the parks. Is staying at the Poly nice, sure; but it is really nice when you have kids who need an afternoon nap and can take the monorail or can walk back to the Contemporary. Even still, a room at the deluxe hotel is only $300-400 a night, which works out to $2000-$2800 a week, not $20K. Plus if you are there to enjoy the parks, you won't spend all that much time in your room. Club level, is just a cocktail bar and light buffet. If I want food or a drink, I can buy it made to order for me--and not have to eat after some kid with a runny nose. Sorry, it's cold and flu season.
Would I do the BBB or pirate thing for a kid sure, but that is no where near the $20K mark. As an adult I enjoy the tours, and have done a couple of them. Once again no where near $20K.
I can't really comment on a private tour guide, it would really depend who gave that tour. I have been to WDW so many times, I wonder if the guides would be of any help, other than avoiding lines. Since I save my time other places, never go during the summer, and am an avid fast-pass user, I don't mind waiting for a ride.
As for shopping. There may have been a time I could spend a ton of money at the parks on stuff. Now most of the things they sell are of lesser quality. I remember as a kid the jewelry store on Mainstreet selling diamond mickey rings, and the jewelry store in the Contemporary have tons of really cool custom jewelry. They do occasionally have a nice item, now; but certainly not $15K worth--what I would need to spend on souvenirs to make up the $20K challenge.
***If they ever rented out the Cinderella castle suite and did a bi-costal vacation with access to Club 33, I may be able to spend that in a week.