How can I help my chubby 4.5 year old son lose weight?

My son weighs 55 pounds and I am really want to change the way he eats. My two other teenaged children are naturally very thin so I have never had to deal with this before. I have already banned all soft drinks and sugary drinks in the house. I have replace whole milk with 2%, and I am thinking of going to skim. I would particularly like to know what kind of snacks a little kid would like to eat that are healthy. I know he really needs to lose weight but I dont want him to feel like he is on a diet.