We did not see a ping-pong table on the Beyond and she is really not designed for kids (imho). Celebrity tends to aim more towards adults and the beyond is no different. There is a rooftop garden which is a great place to have a glass of wine and read a book, but no mini golf. I don't remember seeing an arcade room but to be honest, did not look for one. I don't even remember a basketball court, but could have missed it. We've been on many RCL and X voyages and can only say if I had young teenagers, I'd probably stick with RCL. But that's just me. Only you can decide what your kids will think. Have you looked at the YouTube video overview of the beyond? Might help & you should be able to find it on X page via this link.. Good luck
https://www.celebritycruises.com/cruise-ships/celebrity-beyond