I recommend with kids that as soon as you find out that your child will need glasses that you begin to acclimate your child to glasses in general. Start by showing your child that you wear glasses (if you do).
The right temple style that wrap all the way around the back of the ear help keep glasses from sliding down or dropping off a child's face completely. For babies and toddlers, this Dilli Dalli frame called "Half Pint" has cable temples that wrap snugly around the ears to hold eyeglasses in place.
When your child takes them off, put them back on with a smile, but don't make a big deal about it. If they are really fighting or upset, set the glasses to the side for a few minutes until your child calms down and try again. You'll also want to have activities on hand when you put those glasses on.