I saw this idea on pinterest originally, which prompted me to make a pattern up for my sons! Its a cardigan made from a men's sweater.
The idea had the buttons sewn directly on, rather than having buttonholes, but I really like the buttonholes and the option to open the sweater. Pair it with a nice shirt and tie, and its a really thrifty project that makes your little guy look like a million bucks!
There are two pdf''s. One is the pattern (print and make sure the box is an inch!) and the other is the tutorial. Be kind, its my first one! These are for sizes 4/5 and 6/7.