I think you should tell about the tooth fairy after the last tooth.
About the Easter Bunny and Santa Claus when you think the kids are old enough to understand the traditions that they are symbols of- conversation like this-
"honey you know the story about the 3 wise men?"
"yes mommy! They brought gifts to baby Jesus!"
"So do you know why we give each other gifts at Christmas?"
...blah blah blah and then the inevitable...
"but I thought Santa Claus brought the gifts!"
"Santa Claus is a symbol.. you know what that is?"
..then more blah blah...
"Santa Claus is easier for kids to understand and I thought you were old enough to understand the REAL reason we give each other presents!"
All in all, making your kid feel all proud that they can grasp an abstract concept like that.
Just my few cents!