Brushing before Bed time is mandatory (twice a day).with paste specified for children and brush too.
Wait until age of 13 and if still gaps persist, treatment would be required.
Until all permanent teeth erupt, certain gap between/among teeth will be created and automatically will be eliminated by eruption of further more permanent teeth.so not to worry about gap between teeth until all the permanent teeth have erupted for your kid.I.e. age of 12 or 13 yrs.
Health Tips
get scaling done for him once pandemic subsides and teach correct brusing strokes for preventing calculus formation and maintain oral hygiene.
Luke warm water and a pinch of black salt gargle once a day before brushing at night regularly.