can i cancel immediately without effecting the gift codes?
You should make sure you copy the codes down, before you do it. You probably won't have access to them afterwards.
Also, I don't know why people would even want to cancel. You get $10 Amazon, $10 Fandango, $10 Toys R Us, & $10 Living Social for only $15/month. Who knows, if you cancel, those offers may not be around in the future if you decide to sign-up again. Lock it in now.