I love this recipe, and so do my kids. I routinely drop the 1/2 cup heavy cream to 1/3 cup with no ill effects. I also use part-skim mozzarella if possible. I am suspicious of no-fat versions of typically high-fat foods b/c some of them turn into Frankenfoods, with who knows what sorts of gums and fillers in there, and lots of HFCS to add sweetness (and, I assume, to help with that creamy mouthfeel you're missing by cutting out the fat). Maybe try it with the 1/3 cup and the part-skim, and see how you like those nutritional stats?
If you're afraid of butter, use cream. ~~ Julia Child
As you cook, you enjoy omniscience about food that no amount of label reading can match. Having retaken control of the meal from the food scientists, you know exactly what is in it. (Unless you start w/cream of mushroom soup, in which case all bets are off.) To reclaim control over one's food, to take it back from industry & science, is no small thing; indeed, in our time, cooking from scratch qualifies as subversive. ~~ Michael Pollan