Playgroup Advise

Hey there mummies! Just wanna ask in general, for first time mummies sending your firstborn to school , how long did it take for them to fully adapt? It's been 5 days since my boy started school and he cries every drop off / pickup. Today he seemed a little on the happy side during pickup and was smiling and laughing with his teachers. Also, what can I do to increase my son's immunity? I realised ever since he started school, he seemed to be getting sick more often (flu , cough) . He was down with hfmd on his 2nd day of school and led to high fever and febrile seizure.( A nightmare I wouldn't want to relive.) Are there vitamins / supplements for a 22 month old ? Hope to get some inputs here ☺️#advicepls #1stimemom