Thanks everyone!
To answer some of the questions:
how much does he eat?
Well, he is a 15 your old football player. He *can* eat a lot, if allowed. He gets what he gets, at home. I've never been one to let him eat like a pig, just because. And we have always been very big on teaching the kids to be conscientious of what they are ordering when eating out when someone else is paying ie. water or a soda instead of a specialty drink or milkshake, no "extra" app or dessert, a middle of the road entree instead of the surf and turf, etc. When at someone else's house, my kids are not allowed (EVER) in people's cupboards or refrigerator, if they are thirsty they can ask for water, take a polite helping of whatever is being served and not take more than what they think they will eat, never take the "last" of something until they offer it to everyone else first....just generally being polite and courteous and not act like barnyard animals
So, that being said, I am not worried at all that he won't use his manners and be conscientious about the fact that he is a guest. His friend eats way more than he does...DS is 5'10" and 170 lbs, and friend is 5'9" and about 200 (they just got weighed and measured for end of year testing for football), so the parents kind of know what they are getting into, and DS and friend spend a lot of time together at each of our houses.
Why he won't spend:
I have raised him cheap LOL, so like me, he has a hard time wasting money on junk, whether it is bad food or a junky trinket that is going to sit somewhere collecting dust. I can guarantee that he will not want to buy souvenirs. He doesn't wear t-shirts with logos on them (unless it is Nike or Under Armor or whatever), so he won't even buy that kind of stuff. We gave him $100 for his 8th grade Wash DC trip and he came back with $80 of it. He bought some Sudafed in the airport and I think a ice cream and Gatorade or something one day and that was about it.
We have raised our kids to value experiences, so the majority of any money spent will be on entrance fees to various places. We will cover that for sure, but my worry is that the parents will just pay for along with the rest of the family instead of having DS pay separately (I know we would if a guest was with our family). That is why I want to give the parents a major portion of the money...that way they can just pay and nobody feels awkward. They have (since the original post) told us that they are getting a condo with a kitchen and won't be eating out much.
It's not a matter of whether DS knows how to manage himself (and his money), it is whether the parents will feel comfortable taking money from a kid to pay his portion of the dinner bill or entrance fees when there are three other kids standing there that they are already paying for. I would never take money from a kid....if I invite, I pay, especially if I am paying for my own kids. DS always offers to pay his way when he is with this family...they have taken him to HS basketball games, stop for a snack here and there, went on the train to the NFL Draft a couple weeks ago and had dinner downtown, etc. I have always given DS money to cover himself, and the dad has never let DS use it.
What he *thinks* he needs:
I asked DS what he thought he would need for the week and he said that he would only need about $50 LOL I don't think he understands exactly how much there is to do down there that will cost money!
Additional savings:
I also have to keep remembering that we gave the family a FF code for 40% off their car rental, which translates into a $400.00 savings for the week based on the SUV they are renting. Even though that is money that didn't come out of our pockets, it is money that they were prepared to drop on the rental and now they don't have to.
I think we will go with $200 to the parents, $100 to DS and whatever money he has earned that he wants to bring, plus a gift bag for the family with gift cards for gas, maybe a restaurant, and some little things for the kids, and the FF car rental discount. All together, it will add up to well over $500....geesh. DH and I could do a weekend alone for that much! Lucky kids, I tell you!