Create a fabric mail sorter and hang it in a convenient spot. The version shown here was tailored for out-going letters. Adapt it for incoming mail by including big slots for envelopes and small slots for a letter opener and a box cutter (for packages).
I could totally do this with money-- dollars on a pumpkin then popsicle sticks with bills and coins that add up to the amount. Addition/subtraction sorting - child needs to determine which sticks add up to the number on the bucket.
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