Our first cruise was a Mother's Day gift on the Fantasy. They didn't have any special events or anything but they (specifically the dining staff) really went out of their way to make her vacation the best. She has been hooked since. Have a great trip.
NCL Sun x 2, Monarch OTS, Oasis OTS, Independence OTS, Navigator OTS, Mariner OTS x 2, Sovereign OTS, CCL Legend, CCL Fascination x 2, CCL Glory, CCL Celebration, CCL Miracle x 2, CCL Pride, CCL Fantasy, CCL Freedom, CCL Breeze x 2, CCL Liberty, CCL Imagination, Emerald Princess
a lot depends upon the cruise line. The waitstaff will go out of their way to make Mom feel special, and the menu might be a bit more special that night. You can find out either ask your TA or call the special services department at Carnival. You could always make some "arrangements" ahead of time for Mom.
On NCL, last year we got a carnation since we boarded the ship on Mother's day and then that evening, we had chocolcate covered strawberries on a plate when we came back to go to bed. I put my carnation in the ice bucket right away and every day when the cabin steward filled our bucket, he put it back in there for me. We didn't use the ice to drink, we just put bottles in to keep cool. By the end of the cruise my carnation was still perfect, but couldn't take it off the ship since I thought customs might not like it. I should have pressed it and just put it in my suitcase. PS we had an inside cabin so I know the chocolate covered strawberries were for Mother's day treat since we normally wouldn't have gotten any treats. We cruised the year before on Father's Day and they got nothing.