How out of focus is it? Any chance you could post a copy (cropping so it's doesn't identify your friends)?
If you haven't a good photo to work with, you are very limited to what you can do, and occasionally trying to improve just makes things worse.
Sure, you can use the unsharp mask, and various other tools, but it is limited.
Additionally, if you plan on enlarging, all it does is emphasise the er, not so good bits! Remember the 300dpi too.