For an initial launch it makes sense to go with the far and away leader in the industry. There are ruggedized cases available, so durability shouldn't be an issue. A lot of their potential customers already have iPads, which is another boost.
The obvious choice of otter box came in first: http://www.amazon.com/OtterBox-APL2-IPAD1-20-C4ATT-Defender-...
Second best ipad case was the gumdrop: http://www.amazon.com/Gumdrop-Cases-Drop-Red-Black-DS-IPAD2-...
The otterbox had a stand that people liked (even though it made a clunky cover) and the gumdrop one was great for full coverage (and much better made than the griffin competitors).
Our users weren't as big of a fan but speck: http://www.amazon.com/Speck-Products-HandyShell-Case-SPK-A02...
made our personal favorite. Not as much protection but the stand / carabineer functionality is great!