I talked to Omi's Surgeon today.
He met with the radiologist today and they both seem to think it's a hernia, but still aren't 100% sure.
So, they are going to do a scope through his belly button so they can visually confirm that's what it is. If so, they will just operate right there. If not, and it's fluid, they will either drain it, or just leave it alone based on how it looks. 
Essentially they won't know what to do until they see it on the scope. But, they'll be set up to deal with whatever might come up.
They will call me tomorrow and let me know when we can get in to have it done.

Meanwhile, I think Omi is finally teething. He's drooling a lot and trying to chew his hands off. Those are his main concerns right now. He thinks hernias are stupid.