Assuming you're after fairly rough-and-ready engineering values, I'll try offering some comments:
1. The enthalpy of fusion is a rather weak function of temperature. For most engineering purposes, assuming it's temperature independent is not a bad approximation.
For the rest of the comments below, I have to assume you know how much overrun (that is, included air) you have. Commonly ice cream runs about 25-30% air by volume. I hope you won't say there isn't any, because if you did, your "ice cream" would be more like a solid block of flavorful ice.
Anyhow:
2. Density of a two phase mix, which is essentially what you have here, is often estimated as a volume fraction weighted average of the components. Thus, if you know your ice cream is (let's say) 25% by volume air, you can get the air density at atmospheric pressure and the desired temperature by the ideal gas law. The "liquid" part of it-that is, the actual freeze mix of milk, flavoring, sweetener, and whatnot-could be reasonably approximated by the density of milk, tables/correlations for which are likely available from agricultural extension services, among other places. Put those data together in a volume fraction-weighted average for various temperatures and there you have your density as a function of temperature.
I'll follow with more comments later. Gotta go right now.