Playtime and more vigorous playtime is needed! Want to wear them out? A couple of ping pong balls in an empty bathtub is great for that!

Your mother should probably consider getting a playpen* to put the tree in, otherwise the kitties will probably find it irresistible to climb! We are very glad you didn't get them declawed, as that can cause lots of behavioral issues. Have you tried getting their nails clipped? That's something you can do yourself which can cut down on their destructive capabilities! Electric cords can be hidden (and protected) with paper towel tubes if necessary! Have you tried taking them for walks on a leash and with a harness on them? That might help use up some of their excess energy, and be fun and stimulating for them!

*we used to do that with our Great Dane, as her tail, when excited, otherwise could clear all the ornaments from the tree in a matter of seconds! Your mom likes going all out - so she could decorate the playpen and make it part of the fun!