My family always goes to Disney with my mom and I have done things to surprise her.
This past August, I surprised her with an Illuminations Cruise, which I found on the dis (there were 6 of us from the dis that all chipped in), I have done Fairy Godmothers (I think that's the name, they surprised her with different things throughout the MK), a horse and carriage ride outside of Wilderness Lodge, etc.
When we went on the Disney Dream last year, I surprised my mother each night or morning, when she went into the shower (we had connecting staterooms). I had purchased wine for when she boarded, Disney Cruiseline key chain, shirt, Disney cruiseline bag, etc. I actually got all that stuff before we went on ebay.
Happy planning and enjoy the vacation with your mom. My mother and I were at BWVs for 9 nights, but were by ourselves for 5 nights before my family came. We had so much fun we are doing our own mother/daughter trip next end of August at BLT.
Happy planning!