Okay, my 2 cents:
Doesn't sound like it's going to be easy to upgrade for you since you're trying to price it out and all that. So, why not keep the QSD and enjoy it. You have plenty of time to research all your available options. Let me tell you, there are some awesome "better choice for your value" quick service options out there. Like regular meals! go to allears and scour the menus!
2nd, cancelation is a lot closer to the reservation time, so you can certainly cancel now with no penalty. the sooner the better. I don't know the exact time, but it could be like 48 hours or something, but I'm sure someone will tell you. Make sure you follow up later and be sure you didn't get charged though, because some have said they had problems, but who knows there could be more involved in that.
Also, if CM has your heart, why not keep QSD, but keep your breakfast at CM and cancel the dinner. Save just enough to splurge on that. Again, check prices on allears to see if that price scenario works or even makes sense. If you didn't really care about that, then, no prob to cancel both.
You'll have fun anyway!!!!