the only reason Castro and Chavaz made the offers was because of politics and have a little fun at America's expense

Actually Cuba is very experienced at aiding people in these situations and Cuba's help would have been very valuable (i.e. saved lives).

Cubans may have known Bush would have turned them down, but that is not the point. They were ready to help.

In addition there is the example of Cuba's offer to aid hurricane victims in Nicaragua that was first turned down by the Nicaraguan government, but the accepted as a result of the outrage of the Nicaraguan people.