And to make one clarification - the problem I'm really struggling with is how to store the multiple items bit. I get that if a user only selections (all) or makes a unique selection that its pretty straightforward.

I just can't for the life of me figure out a simple way to store the multiple items piece.

One other piece of information - the items in each of the report filters are all unique - although it would be better if I didn't have to depend on this.