Unfortunately, Coronavirus does not affect only adults, children can also develop COVID-19.
Most of the cases are not showing the symptoms and Covid-19 in children usually have milder symptoms when compared to adults. However, some children might develop severe complications and need to hospitalize.

The symptoms of Covid in children are similar and we list few main Covid-19 symptoms;

If you are suspicious that your kid might have a Covid-19 infection, you should get a PCR test and isolate the kid from family members and visitors. And of course, the kid should stay home until receiving the result of the PCR test. If the symptoms get any worse, you should call your doctor or admit to the closest ER.

Getting Covid-19 again seems to be rare but you have a still possible to get Covid-19 again after the recovery of it.
It is called reinfection. According to the knowledge from similar viruses, reinfections are expected.
This situation is also valid for vaccinated people. If you got the shot of Covid Vaccine and still virus can infect you again and thanks to the vaccine, the risk of severe illness and death decrease significantly.
There is a study called SARS-CoV-2 Immunity and Reinfection Evaluation (SIREN) which was conducted by the Department of Health and Social Care and Public Health in England. The study showed that the possibility of reinfection is decreased by 83% for at least five months due to the responses of the immune from the previous infection.
The results from the same study suggested that cases of reinfection are rare and the ratio of occurrence is fewer than 1% of about 6.600 participants who had already been infected by the COVID-19 virus.
Reinfection is a rare situation but it is significant to take precautions such as wearing masks, handwashing, and social distancing.