This is a very nice fish however it doesn't appear to be a blue gill. I am positive that this is a chinquapin. Although it is simillar but slightly different. 1.75 pounds is still a big Chinquapin. Congrats to your son.
that's a female hybrid bream.. i got a buttload of em in my pond. the grow fast and eat catfish food. in the right conditions, they get to 3-4 lbs.. they are a blast to catch.. and great for kids who get bored fast..
I can't see the marking clear enough without a bigger picture but it does look like it might have a light ring/edge on the gill flap. If so it isn't a bluegill. Either way it is bigger than any bream I have ever caught!