Should I or Shouldn't I?

I'm waffling quite a bit on whether to buy an amplifier that I saw in the Musician's Friend catalog. It's a great deal, but it's still a lot of money. I felt a lot better when my wife said it could be a combined Father's Day/birthday present. So I think that's ok. But there's another dilemma to be resolved. We both think it's important to get our kids involved in music, not necessarily so they can do it for a living, but because, just as there are positive effects from playing sports, learning an instrument teaches a lot of valuable lessons. We tried piano lessons but, like me when I was a kid, they became disinterested very fast. While we were looking through the catalog, we came across a Fender "mini-strat" electric guitar that's just their size. They claim that they will practice intently if we get it for them. They really want it. I've explained about the sore and blistered fingers that initially come with frequent practice and the fact that they'll have to share and they still assure me that they'll practice everyday. Of course, my oldest, the future lawyer, left open a loophole should he need it: "The only days I won't practice are the days I feel sick." This worries me because he was born with a congenital, mysterious ailment that strikes whenever he has to clean his room or do the dishes or any other task he doesn't like. We've tried everything but nothing seems to help. It would be great to get this guitar for them, but not if it's just going to sit around collecting dust.