It sounds like you're really committed to doing the best you can on this assignment and that's great. Be careful not to put yourself under too much pressure, though.
Do you have any chances to shoot High School or College tennis between now and then? If so, I'd do this as many times as possible. Or even go down to the local tennis courts and learn how to read the game from the proximity of courtside.
You need to get familiar with how to shoot forehands and backhands. A forehand shot typically doesn't look the best when shot across net unless you time it for before or after ball impact, like these images:
Trying for a forehand shot from across the net and ball impact, for example, often ends up with flailing arms like this:
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Which I think looks kinda weird.
There are several posts on this board that describe shooting tennis, so give the search feature a try and see what you come up with, then post your images here and see what the members have to say.
You mentioned to me in your email that those familiar with the venue say the 70-200 is all you'll need, and this begs my next question: whom are you shooting for and what are they looking for? I haven't worked a lot of pro tennis, but the events I have covered, there were mostly 400's, both for covering the matches courtside, and especially for working from behind the end lines, like this. No way you're gonna get anything from behind the baseline with a 70-200:
Is the agency you're shooting for looking for tight close-ups or full body shots? FWIW, I have rarely been told to shoot looser on any assignment and in any sport. In fact, most of the images I have had published were cropped even further before being published, so the Photo Editor ended up wanted the image even tighter than I shot it.
Shooting tennis from the side of the court with a big lens like a 400 may see like overkill, but trust me, it can and is done all the time. First of all, like I said above, if you shoot with a 70-200, you'll be relegating yourself to pretty much only covering the action in the near court - you'll be way to loose to get anything on the other side of the net. Secondly, while a loose shot can always be cropped tighter, you also say the only pro body you'll be able to get is a 1D? That's not a very big file, so relying on cropping to get you tight shots might be more problematic.
Edit: I just realized all the shots I've posted are from the first pro tennis event I covered a couple years back, and this was only a month or so after getting my 400. I went into the event worried that the 400 would be way too long, but after a day or so of practicing (during qualifying) ended up shooting 90% of the matches (and about the same percentage of events subsequent to this one) with the 400. I'll only change to a wider lens if I've already gotten enough close-ups of a given player, to add variety.
Again, don't put too much pressure on yourself. At the end of this or any other day, the quality of the work in your portfolio is way more important than the level you are shooting at.
Here's a link to the ESPN photo wire. It gives you a good idea of how tight to shoot and what types of images are their best (they only submit the best shots from any given match, and of these, typically only the best get published or posted):http://sports.espn.go.com/espn/apphoto/wire?id=850
The first time I worked a pro tennis event, I spent hours here, and actually saved dozens of images to my hard drive and put them in a slide show. I watched this slide show over and over again, analyzing where I thought the photographer was positioned, where the ball was, whether they were low or high (some venues have sunken pits on the sides of the courts where you can shoot from), etc. Basically, I tried to reverse-Engineer how each of the shooters worked the match. Then I incorporated what I learned into my first matches I covered, and afterward, compared my shots to the best of what I had seen, and posted here and on another sports board for honest critique.