My first was a novella as well so I do understand what you’re saying. Just be aware that the length will be a turn-off for agents. That doesn’t mean it’s impossible, but it’s well to know when you’re going in with a disadvantage and finding an agent can be tough at best.
I found the part about tearing his family apart a little confusing and puzzling. While you don’t really want to make it longer, perhaps you could state that a little more clearly.
Many years after declaring hatred for his father, Kenneths son Ethan has cut ties with his family. In hopes of brightening what may be her dying husbands last Christmas, Isabelle convinces Ethan to return home with his wife and sons.
I think this needs some polishing. the part about Ethan hopefully could be simplified. It seemed confusing to me. The many years part I didn’t understand and it seemed to imply he only recently cut his ties which I have a feeling may not be what you meant. Also is Ethan only Kenneth’s son and not Isabelle’s? That seems to be the implication. Wouldn’t something like: Their son, Ethan, has long since cut his ties to his family say the same thing more simply? But maybe not. As I said, I wasn’t clear on the situation.
The other thing that bothered me was suddenly making the query from her PoV saying she wondered. I’d take that out and just say A long held family secret may thaw Ethan’s heart–but that’s me. Keep in mind that it’s all a matter of opinion. 🙂
And your story sounds interesting.