I wouldn't worry about it. I don't prewash, unless the fabric is red. So, when I make quilts that have red in them, that fabric has already been washed. The rest hasn't. And I have never been able to tell when it is all quilted and bound.
It just all comes out even enough by the time the quilt is sandwiched and quilted. Or at least it always has for me.
I'd suggest that you just "carry on" and try to stop worrying about it. Your quilt is just beautiful, and the boy who gets it will love and treasure it. Good choice of pattern and fabric!!
Dina