You are due for dissappointment if you think you're going to get matching footage from these cameras. You might really whack out the video with grain and other degradation effects, and you might get away with it, but otherwise you are going to have three video streams which just scream out 'different camera!'
I did the same thing, but with four cameras...two DVX's( shot in 24p) a VX 1000 and a TRV 6...I was able to fudge the look a bit by adding a blur filter and adjusting brightness and contrast...you aren't going to come close to matching the beauty of the DVX but you can make the others interesting enough to reduce a startling night and day difference.
Do a search for Jeremy Camp in Twenty Four to see the results.
I've done many multicamera shoots. Here are some thoughts.
First, WE (i.e., video afficianados) are more apt to notice the different look of cameras, not the average viewer (assuming the DVX is set to 60i like the other cameras). The average viewer is too busy watching the content to attend to subtle changes in the color or sharpness of the picture. Also, as you switch camera angles, the viewers point of reference changes and slight differences in the look from different angles are not noticed. Now if the main performer has a bright red shirt on from one angle and a dull red shirt from another, that's different.
If you have some obvious differences like the one just mentioned, there's a possible solution. In your non-linear editor, make color correction adjustments to each file to try to bring the colors as close to one another as possible. Have a TV or monitor hooked up to your camera so you can see how each file looks on a TV. Don't trust the "look" on your computer screen. The computer seems to minimize the differences. I once used cameras that were quite different in look and never checked them on the TV until it was too late.
A final comment. I just did a wedding outdoors on a moderately bright early evening. I used my DVX100A, my trusty Sony TRV310 (5 years old-just had the heads replaced), a borrowed one chip recent consumer Panasonic, and an old Sony Hi8. I was astounded that in that well lit situation, the footage from the three digital cameras blended so well, I had to do no color correction! I had to color correct for the Hi8 camera, and even with that, it looks quite inferior to the digital cameras. I've had previously used these three digital cameras in a church, and the colors looked different from camera to camera in that indoor setting. So when I went to view them on the TV I was delighted to see how compatible they were for this outdoor shoot.