I recommend a warm rinse, as hot is bad for babies. My main concern is drowning him/her, so set it as small load. It'll probably get knocked around enough to get fully cleaned without the drowning factor.
Children, on the other hand, can better handle the heat and know how to hold their breath, so you can go warm-hot, though warm is probably better for it. Based on their age, set it to medium or large load.
One method I practice is to keep my children tied up before getting them all hot and wet, this way they don't squirm around and break the washer.
