Amumu support is a lot better than Shen, imo. But there's a reason supports are supports, and Shen is a top laner. I'd also recommend avoiding Shen support under any circumstances.
Your solo champs need a bit of work. I don't recommend playing vayne unless you have the right runes to stand a bit of poke and knowing how to self peel. As for top I think you should stick with renekton he is a good top laner usually a big bully so keep going there. As for vlad I'd say he doesn't belong mid so MIT want to get a new mid player