Hi, Magan!
MagicBands are wristbands made of a smooth rubberized (non-latex, allergy-friendly) material and are available in several color choices. They do not stretch or slap on or have a clip, but they are fully adjustable (much like a watch band or belt). MagicBands fit a wide range of wrist sizes, including those of young children and larger adults. If your mother experiences swelling due to fluid retention, she can simply adjust her MagicBand to fit more loosely and comfortably.
My family and I wore our MagicBands during our trip last month and we found them to be very comfortable and convenient. We would take them off before going to sleep and then put them back on in the morning before we left our resort hotel room to head to the parks. MagicBands are waterproof, so there's no need to remove them while swimming or on water rides.
Because children under the age of 3 are not required to have park tickets (i.e., they are admitted free of charge), they will not receive MagicBands.
I hope this helps! Please visit us again here at the Moms Panel with any other questions as you continue planning your trip.
Wishing you a magical day!