I had a big, long post written (in my head) debating the position of using the TMNT as a basis for your (presumably MAME) cabinet, but am feeling lazy today.
Most often the "use existing cabinet" option is presented as the "quick and easy" way out (which it is), which sadly comes across as some kind of copout.
Then again, having a single cab run an emulator instead of multiple dedicated cabs running original hardware is pretty much as quick and easy as you can get.
From my personal POV, I would suggest using the TMNT as a basis for your MAME cabinet unless you:
1) want to do something unique with your cabinet design (if you're just going to build another UAII or Lucid clone, don't bother) or go with a woodgrain finish (my original plan)
2) want a woodworking project to involve your kids with (my twins are 11 years younger than yours so aren't ready for power tools, but are happy to clean buttons and playtest)
3) want a woodworking project for your own benefits (including a sense of accomplishment), away from everybody else (I fully understand this one)
If, later, you want to change things up and build a cabinet, you will still have that option ... along with all of the experience and equipment from your first build.
From your posting, it seems as if your have built things with wood before, so perhaps would not get quite the "hit" off of building your cabinet as the first-time woodworker.
Good luck with whatever you choose.
Cheers.