That was helpful Moondog Why do you have to be so rude?
My DS is Oliver but usually gets shortened to Ollie. However Olly and Oli are lovely too. I would go with Pasturesnew suggestion of naming him Oliver and letting him decide whether he wants to shorten it and if so what to shorten it too.
Our Oliver chooses "Ollie" for a short version - though mostly he seems to stick with his full name except when he's playing football. I guess having less syllables is easier when you're shouting it across a football pitch.
My birth name is Oliver and the shortening of it to Ollie etc. is a big deal. I've been treated like an idiot who doesn't know how to spell their own name for writing Olie. I find the difference between Ollie and Olly to be as great as David or Peter; as the correct spelling of the abbreviation is a matter of opinion people naturally assume their version is correct. In conversation most people say Ollie and to use Oliver is perhaps a little old fashioned. I am now Olly.