Get this book. It's the best resource for not only keeping sound from getting out of a room, but also for optimizing the sound in it. Given your constraints it sounds like resilient channels in your ceilings and walls may be your best option. Any half competent contractor or even a handy layman can follow his simple instructions. In any event, you'll learn a lot about what and what not to do to create a good sounding room. I found it very approachable and educational. Best of luck.
https://www.amazon.com/Premium-Home-Theater-Design-Construction/dp/B0041SUL2E
https://www.amazon.com/Premium-Home-Theater-Design-Construction/dp/B0041SUL2E