I very much agree with Chinadog on this - if you can get adequate lighting for hornwort or elodea, your water will be so much better and will ease maintenance, too.
Also, with my own experience with Icthyosaura alepstris apuanus a land portion of a tank would be a waste of space. Mine occasionally haul out on their java moss covered styrafoam floating island, but it is rare. I think you would be better off dedicating the whole tank to water with just some floating islands. The more water you have the more stable your water conditions.
Best of luck, and be sure to post pictures when you have your tank set up!
HJ