No – as far as SP capabilities are concerned you have what you need.
As far as WP capabilities go then I can not be certain but I can think of no reason why you should be thwarted. My own personal knowledge of multi-site is not really up to much diagnosis but I would have thought if you were the main site admin there shouldn’t be an issue.
Steve (Mr Papa) knows a little more than me regarding MS so I will ask him if he has any ideas.