I'm not going to ask for any $$ back because it was the right thing to do at the right time.
Don, if you become a self made millionaire I'll only ask that you teach me to be the same
Until then, just weigh your options very carefully. PP was right in that fact that there is a lot to know about salt water tanks, she was just pointing that out. No offense intended I'm sure. As for the question.. it was a simple one and a simple answer could have been provided or researched. Either way it doesn't matter.
If you feel that a tank is in your daughter's best interests I'd double and triple check that. Have a sit down with the family and some nice glossy magazines with beautiful pictures and let her decide and you do the research on the care requirements. The sit down is actually the best part.
If it is doable, the it is, if not move on. If she chooses a fish, then tell her "I'll check" as opposed to "ok" and trying to work out something that probably won't work out. Then move to plan B.
Special considerations:
Will she be able to take care of the tank?
Would education be a better option?
What special care does she require that "make a wish" could provide for vs something material.
I'm not trying to dissuade you from the tank, but what would benefit her the most in her life?
Earlier I said if this was MFK....
Go BIG or go home. Think about it. If MAW could couple their services with say ... Mike Holmes, or another group that has a philanthropy division, you just may get more coming to you than expected

Geeze.. Red Hot Chili Peppers gave millions to save the whales! Get Nickelback or Avril Lavigne to throw a charity concert!! How cool would that be to attend and get the $$ your daughter may need for a life time
The board I don't believe is being overly critical, I think they're just warning you about what lies ahead if you pursue these options and offering opinions.
Take care
J-P