User Steven 58 summed it up well. Monitor the apps you do use, and after some time decide which ones you use/like and keep those and clear out the ones you dont. If you are unsure if you should or should not delete something just ask here and/or do some digging online to find out if it is a necessary app.
Clearing data and cache regularly is a good part of general device maintenance. Once a week or once a month depending on frequency of use (more use = more often) is a generally good idea.
Also, im not sure if i would consider facebook to be an educational platform, but it is not my place to advise you on what platforms your children should/should not have access to. However I would say it is a good idea to monitor their use and frequency of use of any applications at such a young age.