Airport

That's a good idea, but is prefer the rocket ship with launch pad and station with astronaut skins for barney and homer. Imagine the huge rocket in your town, it would be sick and when homer does his going into space task the rocket launches out of screen and reappears when task complete. Here's a short list of combined tasks I've come up with, feel free to add more if you can.

Barney:fly jet pack drunk-1hr
Clean himself up-4hrs
Work out-8hrs
Do astronaut training-12hrs

Homer:be lazy-1hr
Go into space-7days
Work out -8hrs
Swimsuit competition-12hrs

Combined tasks:work out together-12hrs
Space simulation-24hrs

That's all I can think of ATM.