As an American, I prefer these two to 'habits', though 'habits' is certainly acceptable. I think 'behaviors' in particular is very customary in this field.

If, as it appears, this is a list of accomplishments achieved, brevity would seem to be desirable. In that spirit, I offer this suggestion.

"Improved", as noted in the discussion comment, could be another viable verb choice. "Reinforced," though, is closer in meaning to the original "fortalecidos", and more contextually appropriate than "strengthened" (since we talk of reinforcing habits, not strengthening them). Which verb is preferable depends on whether the author is saying that children needed to be taught the healthier alternatives, or they already practiced them to some degree but just needed reinforcement.