Glx9 ,
Maybe you could try this:
Go to one of the high end acoustic treatment web sites and gather room treatment info. Call those co's and ask their advice about "parent friendly" treatments and colors.
Print out this thread and gather all your info and make your presentation to the folks. Start with just a lil trap here and there or maybe some new curtains or furniture. Your room doesn't have to look like a studio.
Lastly,
Explain to them that you have a world class system there and that they could enjoy the money spent better if they could hear the equipment better and not the rooms reflections.
Good luck!!