Lots of great ideas-- and you can always do the mother/son dance! I'd say come up with several ideas and let the boys vote. Next year do the same and let the girls vote. They may choose something besides a dance.

what about a sports themed dance-- with both mom and son wearing their favorite sport jersey-- showing a sports related movie in the back-ground--
or an art night where mom and son paint a ceramic project together-- we have several in our area that will come to the school--
Also a deal or no deal night where mom and son work together to get picked to play and then to pick the cases. Good luck with whatever you try-- I'm sure the moms and sons will love it!

How did you do both events the same night?

We had a mother/son magical evening the same nite as the daddy/daughter dance. It included pizza & a magician

At our school we have a mom son bowling event at the local bowling alley. It is usually on a saturday afternoon in the winter, both moms and sons really look forward to this event. We have bumpers set up for the smaller children.

I agree. something that the mother and son can do together. You can also model it after the amazing race where the two team members had to do different tasks together before they could move on to the next phase.

Have them start at one point and move about the different tasks picking up something along the way. If they complete all the tasks successfully, they get something.