My best tips are:
Sunburn:
Bring a long sleeved light-weight shirt with you to Disney. If you start to burn, you can wear it over your summer clothes to keep it from getting worse. If you do get a bad burn, wearing a tight fitting t-shirt works well. It acts as a temporary "skin" that moves with you. A loose fitting shirt on the other hand, will brush over the super-sensitive skin causing pain. Wear the tight shirt under your normal clothes and when sleeping.
Feet:
Before trip prep:
Stand as much as practical. Put your laptop on a counter, bar height table, or in a pinch an ironing board. Force yourself to stand to use it as much as possible. Your arches and ligaments will stretch some as it adjust to holding you up. This causes a lot of pain initially. It will be gone in about 6-8 hours of standing. Better to put yourself through this before you leave.
On your trip:
Follow the following mantra:
Don't stand when you can lean on something.
Don't lean when you can sit.
Don't sit when you can sit with your feet up.
It's easy to just stand and wait while someone else is shopping or in the restroom, but finding a place to sit or a wall to lean on might mean less foot trouble later in the day. Is it worth it to stand in a 30 minute line at the turnstiles in the morning just to get in a few minutes before others? Or, might it be better to sit on a bench and wait for the turnstiles to open and then find the shortest line? Alternately, you could take turns having one of your party wait in line while the rest sit.
Lastly, avoid overdoing it early in the trip. If you get to a point where your feet hurt even while you're sitting you're overdoing it. There just isn't enough time overnight for your feet to recover - though the lotion, massage, and ice bath could help. Later in the trip, it won't be an issue - they'll just hurt some and you'll be used to it. It's like having a annoying headache and to be honest, I've never left Disney without a footache.
