Hi Davina,
Thanks so much for visiting the Disney Parks Moms Panel with your question. An extended family holiday for a large group sounds like so much fun! You are smart to be thinking about your planning now.
March is a lovely time to visit. The high temperatures are around 26 degrees Celsius, which is quite comfortable and not as hot as it gets in the summer months. Spring Break season does typically start in March in the United States, but generally starts toward the end of the month of March and rolls into April. It tends to peak around Easter, which is April 5 2015. Therefore, I suggest that you plan your vacation for a little earlier in March if possible.
You will probably be visiting during the
Epcot International Flower & Garden Festival. This is a lovely event which includes gorgeous topiaries, outdoor kitchens where guests can purchase delicious treats, and the Flower Power Concert Series with classic music acts. The specifics for this event are not yet announced for 2015; however, you can look at the 2014 information for an idea of what might occur in 2015.
You should also start to consider where you would like to stay with a group as large as yours. If you want to stay at a Walt Disney World resort, you are going to need to book more than one room or villa. This would be a good place to start your planning, with choosing your resort. You can find information about the various
Walt Disney World resorts online.
I hope that these thoughts are helpful for you as you begin your planning, Davina. Please do not hesitate to ask if you have any further questions.