Hi Andy, I was in Cumbuco recently with a friend and her 18month old daughter. The only thing we struggled a little to find when we ran out of them were swim nappies. You can get them, but we had to look in a few places, so take a load when you go. Apart from that minor problem everything else was plentiful and easy to find.
Health wise, it's recommended that the baby has a yellow fever injection but it's not really necesary.
I was there last december with 27 month child. No problemo. Don't forget to put sun block though!
I was in Hotel Golfinho: big pool for kids & wife (+ kids pool) just in front of the spot.
Very nice and secure.