Tablets are great for a business environment. Unfortunately, though, if you are set on using Excel, that does not exist yet for Android or iOS tablets. If you don't care if its excel, you may want to look at Pages or even Documents to GO
. Its not a perfect solution but it can work.
The other option, which is becoming more and more popular, is to hire a designer to create a custom app for you that can then be used to automatically synch the data to your servers. This would probably be even easier for you.
Finally, with Windows 8 coming out, you may want to see if there are some good and affordable Windows 8 tablets on the market soon. Then you have full access to a computer that you can run any Windows app on. I am not 100% sold on Windows 8 as a desktop OS, but as a tablet OS it is quite nice.