You might be better with choosing a different park stradegy. Go to the parks early and then take a break at the resort for the afternoon. Then, he can have a good nap and elevate his legs. Now, go back to the park for the evening. I know two commutes suck, but in the end this would help him the most. This will have the side benefit of not being in the parks in the heat of the day.
Also, give some thought to compression socks. This should help the swelling stay at a minimum. You will probably have to help him get the compression socks on and off. You should have multiple pairs. They're a little expensive, but they will help. You can hand wash a pair and let them hang over the shower rod to dry each day.
Give serious thought to using an
ECV if you haven't given that much thought. Let him practice. You may have to help him yourself at times with the
scooter.