Full amount of heavy cream needed?

Cait0312. Agree with Aargersi's suggestions.
But/and here's another approach.
If the recipe interests you enough to to be thinking of serving it, maybe make it one time as written to see what it's like. Even a test batch smaller than full size.
Sometimes the combination of ingredients gives more flavor or texture than the parts individually suggest just from reading.
After eating it one time, you can decide if you really like it or want to modify it and, if yes, in what direction.

It seems like a matter of taste, honestly you could leave the cream out and have “Not Creamy Tortellini Soup” … if you’re worried it will be too much I’d try adding it 1/4 cup at a time and taste after each addition.
Half n half would bring the volume up with less creaminess as well