I agree the lion shouldn't be a problem with kids, Ram Puppy. I've got two girls (admittedly, boys may be different) ages 5 and 8 and it's just not a problem keeping them from putting hands in the tank and never was. By the time they're tall enough for it even to be possible, they understand enough to be able to put the fear of God into them about how much it will HURT if they put a hand in with the lion. Tell them lions especially like small fingers.

May even be a good thing to have something in there to give them pause. After all, even if the most dangerous thing you have in the tank is Nemo, you don't want them putting sticky fingers in the water anyway.

Centerpiece for a 100g reef...hmm...this shouldn't be hard but I'm having trouble coming up with an imaginative answer. Cardinals come to mind, like a school of Bangai or Pajamas?