On the way to Key West stop by Robbies and feed the Tarpons.
http://www.robbies.com/
As for a Hotel in Key Largo you can try the Marriot. Nice place and a good restraunt is just next door (Sundowners). Make sure to be there for the sunset, hence the name.
Hotel website:
http://www.marriottkeylargo.com/
If you have the time Fort Jefferson is great, you can take an ferry or sea plane from Key West. Further info located below
http://www.vacationdepot.com/drytortugas.htm