(A moderator may want to move to the Orlando forum as there may be WDW people who watch that one more than this.)

I am not aware of late day discounts for admission. You may want to consider going to an e-ride night at the Magic Kingdom. However, it actually costs more because you have to pay for the privilege for staying after normal hours at the park without much of a crowd. Here is a site with information:
http://allearsnet.com/tp/etik.htm

That site also has good discussion on other WDW matters (including tickets; don't know about the golf courses).

You can see a fair amount of Epcot and MK, some of MGM, and very little of AK in the evenings (such as after your convention ends in the afternoon). Pleasure Island is open late, of course (I recommend a stop at the Adventurer's Club for some good improv comedy). If you can, try to stay at least until late Saturday so that you can do AK that morning.

Between the Wyndam and Dolphin, I would choose the Dolphin (a Westin I believe) due to its location (walking distance to Epcot and Boardwalk, boat to MGM).

Have fun.