Is there a reason they can't input on the iPhone/iPod Touch? It seems like the iPad (or frankly, any tablet) would be tough to enter data in unless you're sitting down.
Much easier to have a large 1024x768 screen than try to fit everything in a tiny 480x320.
Update: Just noticed you're across the bridge from me. If you ever need help on the data entry web apps, let me know. I'm working on a similar type thing for a group of medical imaging centers locally (Palm Harbor, St Pete, etc). That's actually what I have the Droid for.