I'm not too bothered. If you want the characters to interact before everything starts to happen, I'd say start with school, although I can't really see them as being friends before the whole contract thing, while if you stick with the original plan, we could have an introductory post for each of them, then you could have stuff happen and the contract signing however you had it planned.

I'm happy with either, but I'm leaning a bit towards the second option.