Why is killing him even an option. That's loving stupid.
•You can't give the doggie to your grandparents.
•You can't keep the doggie.
•You can't try to hide the doggie.
•You ask for our advice, yet protest that it's not what you want.
Bullet point #4 pretty much takes out all your options, including putting your doggie to sleep. And how could you afford that, anyway?
So think of something, and stop posting here.