How fast is your water leaking?
If it's leaking real fast, I'd drain as much water from the large tank as you can into the smaller ones, move the decorations, filters, a handful or two of gravel for each of the 10's, and anything else you can move without making a huge mess into the smaller tanks (split as evenly as possible between them). Then, move the fish.
If it's leaking more slowly, you should try to cycle the 10 gallons as much as possible before moving the fish into them (move the decorations, some gravel, etc. Wait a couple days and then move the fish). Also, move the fish only a few at a time if you can and wait at least a couple days between fish additions. This gives the bacteria in your 10 gallons a chance to catch up with the new bio-load. Of course, all this is assuming it's a slow enough leak.
Once the 30 gallon is empty, you can try to fix the leak. After you've fixed it, fill it up and check for leaks. If you don't see any, leave it full (with no fish) for a week or so, just to make sure the leak really is fixed.
Another thing you could try. When I moved recently, my LFS from my old location suggested I put a big black trash bag in a styrofoam container. He said to drain as much water out of the tank as I could into the bag, put the fish in the bag, tie the bag (leaving some air at the top for the fish to breathe), and finally put the lid on the styrofoam container. You could move your fish into something similar while you wait for your new tanks to cycle. I've heard of people putting a filter and a heater on the side of stuff like this at night (with the bag not tied and the styrofoam container open) and (successfully) keeping their fish in this kind of set-up for a week or so while they're travelling long distances during the day.
Hope this helps! Let us know what the outcome is!
