Since the basics have been answered let me ask the other questions...
First off, sorry to hear about the ALS, my friends dad had it and its definitely not fun to live with... But how much experience do you and your daughter have fish keepers? Not much? A lot? Because while not difficult to keep, i wouldnt say its a beginner fish...
2. When the time comes that you can no longer care for the fish at all do you have plans for them? Since puffers if kepts happy and healthy can easily live for a decade or more...
3. How exactly are you doing water changes? Coz as mentioned above, dragging buckets back and fourth is no fun on a 180G+ tank weekly when you need to do 50%+ water changes...
4. As these puffers do like substrate and decorations to keep them from getting bored, are you guys prepared to setup and maintain a tank like this?
If you can get over all the above, they can be very rewarding fish but depending on you and your daughters level of commitment / passion for the hobby it can very quickly go from enjoyment to a chore with feeding and maintenance...