Since repeating 2nd grade would make him one of the oldest and since he does not appear to be athletically gifted and he is well-placed academically and well-adjusted socially, I would not recommend repeating 2nd grade.
However, my sister had some regrets accelerating her DS in elementary due to high school team sports considerations. Her DS is an adult now but was 12 when he started high school and 16 when he started college. In his case, he was always obviously talented athletically but on the small to average size for age. As such, he always did well in sports or anything requiring athletic abilities even in comparision with his grade-mates who were two years older. However, once he got to high school, he could not compete with kids who were two years older and much larger and also athletically talented.
