Yea... not really sure how you are going to make this work every week for the reasons already stated. Even more so with little community involvement in the matter. Interest will die down quickly if you don't get all the teams (and their members) somewhat involved in the decision making process of MVPs.
If you still want to go for a similar idea though, I suggest having each team select one player from their team each week that they think deserves to be their week's MVP, who better to know who contributed most to the team that the team itself right?
That way you would end up with a list of weekly MVP's for each team. By the end of the tournament, the member from each team that has the most MVP points gets put into a pool of top MVP players.
Then from there, a select group of admins/captains/trusted judges (whatever you prefer to use) try to make an honest and educated decision on who they believe deserves the ultimate MVP prize. (This group of judges would also serve as a filter for the teams that just kept on nominating the same person as their MVP every week to give them a chance at a free prize. This would make sure that only truly deserving players end up with the prize.)
If you are really set on throwing out several prizes this season, then maybe you can use the same idea, but evaluate the results every 3 weeks, and have 3 accumulated prizes. This way, consistency is also rewarded rather than just having a lucky day.
