You could head up to sipi falls for the weekend. Its a 4 hour drive from kampala to mbale and another 45 min from there, but on the best roads you'll find in the country so it's not too bad a trip. Sipi falls itself is very scenic, located up in the foothills of mt elgon. The falls are all pretty close together, and it is a great site to visit if you have limited time since everything can be seen in a day. We just spent a weekend there and it was very relaxing. The lodge we stayed at (sipi river lodge) was a little on the pricey side, but it was well worth it, simply for the hot showers alone. The food was good, although we did half board so we can comment on lunch, and the staff was very helpful and guided tours to all the falls. I was even able to go flyfishing, something I did not expect during my trip.
Enjoy your time in Uganda!