Nice gift!
You've gotten a lot of opinions already. I'll add mine to the mix, but just wanter to add that all of the moderates are nice and I think you will be happy whatever you choose.
We have stayed at all of them except for CS.
Our favorite is CBR.
The rooms are bigger than the other moderates.
Even though it is a large resort and spread out, it is connected with nice walkways. There are a lot of nice sand "beach" areas with places to sit and sand to play in (NOTE: you can't swim from them). There are 7 quiet pools in the resort. As was already mentioned, the food court can be noisy. CBR was the first moderate built and the food court is maybe a bit small for the size of the resort. The buildings that are closest to Old Port Royale (where the food court is located) are considered Preferred locations and are an extra charge.
Here's a link to the CBR page on the DIS, which includes a link to a map of the resort.
One thing I remember at CBR is that if you are on the beach in Martinique or Trinidad North, looking toward Aruba, you can see the highest fireworks from Epcot (Aruba is actually just behind the American pavilion).
POR is also one of our favorites. Some people have noted that some of the paths are bumpy (we didn't notice ourselves, but my DD likes bumpy).
We really like the food court at POR and usually go there for a meal on each trip even though most of the time in the last few years we have stayed at OKW.
Here's a
link to the POR page. The DIS website lists the average room as the same as CBR, but I don't think tha't true. As far as I know, CBR is larger. There are 5 quiet pools for about the same number of rooms as at CBR. The food court is much larger though - at least the seating area.
A nice feature that was already mentioned is the boat you can take to DD. Very relaxing (is wheelchair accessible).
PO French Quarter is a very pretty resort. Much smaller than the others (although at over 1000 rooms, it's not exactly a small resort). As was mentioned, there are elevators, but you may not necessarily be close to an elevator and may need to backtrack to get to one. I believe there is only the one main poll, but it is very large.
You can also take the boat to DD.
Here's a
link to the French Quarter DIS web page.
I don't know anything about CS except what I have read and seen from the outside. Here's a
link to the DIS page about CS.