It is OK for a 7 year old boy to wear diapers all the time or anytime.
A 7 year old boy and 8 year old boy or any kid of any age should wear diapers full time or all the time as diapers are much more convenient and more comfortable than underwear.
Size 7 diapers will fit an average sized 7 year old boy.
A good size 7 diaper that is very absorbent that I would recommend for a 7 year old boy or other kid is a Gentle Steps size 7 diaper which gets very thick when wet.
The Gentle Steps diapers are very absorbent and comfortable and will fit most kids from 5 to 10 years old.
If the size 7 diapers won't fit then you can also have the 7 year old boy wear a size 8 diaper.
Size 8 diapers are available in Pampers Swaddlers size 8 diapers, Huggies Snug and Dry size 8 diapers, Parents Choice size 8 diapers and Huggies Little Movers size 8 diapers.
