Suggest you buy "Images of Dorset Country" by Roger Holman/Dorset Books because it will contribute to your ideas but also because has some much better photographs than you might expect from this sort of publication.
I've got to know the area quite well because we've rented a house on Sandbanks for a week nearly every summer for the last 20 years, and quite often Photography has won out over Monkey World and Poole Park as a means to occupy my time (surprise). You might like in addition the deserted village of Tyneham ( get there early or on a weekday) and also the sunset over Poole Harbour from Sandbanks itself. There's also quite a nice view east from the bridge on the S edge of Wareham just at or before dawn. There's a couple of these in the "English Landscapes" gallery of my web-site www.photography001.com . You'll spend much of your time on the coast though.