Having changed the diapers of both (my much younger brothers are circumcised and my friends' sons are intact) - I have to agree with everyone else that cleaning intact babies is MUCH easier! The foreskin makes the penis all smooth so there are no ridges or anything to have to clean behind.
The only person who should EVER retract the foreskin is the boy himself. If he becomes retractile before he's old enough to pull his foreskin forward over the glans (aka - if you change his diaper and notice that his foreskin has pulled back which is very rare, but it can happen) then you should pull it forward over the glans again before putting his diaper back on, but you should NEVER pull it back and you should never let anyone else (other than your son, of course) pull it back either.
The foreskin is fused to the glans like fingernails are fused to the fingers. Just like nothing gets under the fingernails without quite a bit of pain and force (the part that's fused at least
I'm not talking about the bits that stick off on the end - of course stuff gets under there!), nothing gets under the foreskin either.
love and peace.