Ok..in all honesty...comeing from a 22 year old (me)...
Pleasure Island is neat...if you are into clubbing. I know a few people who really dont dig that scene..so of course..you have to look for other options...
Where are you staying? This would really help me come up with ideas, since i know the area pretty well and can most likley tell you what I have done for a "special" time at WDW...
Some other things that come to mind are getting him his favorite food at his favorite country in the World Showcase, Perhaps setting up a picnick for 2 somewhere (there are tons of places you can do this), if he likes fireworks...finding a nice place where you to can embrace and watch the shows...
Keep in mind that 95% of what makes a trip "special" is the person you are with...seeing how you are so concerned over him having a good time..I am sure he will be more than happy this trip...because he is with you...