One of my friends has a beautiful daughter and at age 4 she's only a couple inches short of my arm pit. The doctors project her to be 6'5. Another close friend has a son that just finished his freshmen year in high school at 6'0 218 pounds. The doctors project him to be 6'4. Although it's too early to tell what their interests will be in life should these parents encourage their kids to excel in athletics?
Absolutely they should. These parents would be doing their children a disservice if they didn't push then towards athletics. There is no guarantee that these kids will excel at or even like sports, but their physical stature suggests they should at least give it a try. Sports would undoubtedly help these kids with their social development by providing an environment where they won't feel awkward. Their size will be looked upon as a benefit and an advantage as opposed to a physical oddity. Kids can be cruel and when there's something unique about you they tend to make life miserable. At least with sports there's an opportunity to accentuate the positives.
You can't always let kids just be what they want to be. If a child has a voice like an angel you should encourage that child to take vocal lessons. If a child has a vibrant outgoing personality you shouldn't encourage them to be an accountant. Parents should guide their children towards activities that give them the best chance to succeed in the future. What's the worst that could happen?