Yes balanitis is pretty common in toddlers.
Balanitis is most common in toddlers who are in diapers full time as the diaper can cause the irritation of the penis and penis head which is what balanitis is.
Also it may not be balanitis at all if the toddler is wearing diapers and gets a diaper rash.
I have a 2 year old boy who got a rash on the head of his penis and side of his penis and it turned out it was a rash caused by the wet diapers as he slept through the night.
I started applying diaper rash cream to his penis before putting him in a new diaper for the night and he stopped getting the diaper rash on his penis.
However even when toddlers are potty trained and not wearing diapers they can still get the balanitis by their underwear or other clothing causing irritation on their penis.
The balanitis can also occur in kids, teens and adults and especially if they are uncircumcised.