hahaha well roxy, cruelty to a few snails is a lot better than being the cause of hundreds of organisms dying right?
As for your snails, decide now if you want them or not. If you decide you want them now but change your mind, you are going to have one hell of a time getting them all out of your tank It sounds like you have spend snails by the size you mentioned, and if you got them without buying them then all the more likely that they are pond snails. They breed very rapidly and will soon look like a plague or infestation in your tank if left unchecked.
So as I say- choose now and make sure you think it through, or you are in for a pain later on.