If you land at 11:30, I would plan on the travel to your hotel, and check-in to take you to about 1:30.
It will hopefully be quicker, but I always like to plan more time. Then if it takes less, I feel like I saved time.
1:30 is still pretty early, and you have a lot of options.
If you do DME, you bags will not show up in your room untill later. So I would suggest packing what you might want/need, in a carry-on bag (such as swim wear, hats, sun screen, etc.).
If it is nice out, you might want to relax, go for a swim, and then order up a pizza and hang out in your room.
You could go to a park, and if your staying 5, 6 or more days, the marginal cost of extra days is only a few extra dollars.
Illuminations or Wishes might be a great to see.
You can go for a nice dinner (just be reallistic about the to and from travel times). If you don't go to a park that night, you might not mind spending 2 hours or so over a nice dinner.
Chef Mickey's is always fun, to get you in the spirit of things. I don't think the food is that good there, but the character interaction is fun.
What every you plan, make sure it is what you want to do. Plan reallistically for the amount of time it will take, and you'll be off to a great visit to WDW