My Mom and I were there for Mother's Day this year. They do give carnations at each park. At Epcot, they take a free family photo, similiar to the MVMCP pictures. At certain restaurants, you can order a corsage for your mom to be delivered at the table. I did this at Cinderella's this year, they called up from the front desk when we arrived (with a special code word) and the box was sitting on the table when we were seated. She was shocked! They do require a credit card guarantee on some of the restaurant reservations. We've gone around this time the past 4 years and it's a great time. Weather is starting to get hot (low 90's) but very little rain. Crowds are on the low side. Flower & Garden Festival is in full swing. Our AP's expire May 10 next year, so we are going the week before.
There is usually a Mother's Day Brunch in EPCOT. It requires a PS and credit card guarantee, but is a wonderful meal. Last year it was held in the former Millenium Village.