+ Most projects offer tangible rewards (posters, booklets, figurines, keychains, tees-shirts etc.) that are just cool to have for any self-respecting geek. Unfortunately you're a software enterprise so it's not that evident for you, but I'm sure you can be creative in that space.
You can blog about your progress, you can offer adspace on your page which might sell better than a name/company in the readme.
Also, you're offering a mention in the README as a bonus - which is a good idea. But IMHO you should consider also having a separate DONORS file (or similar) which will list the names of anyone who donated and still be part of the project. Even such a small gesture will help people bond to the project and feel like they're a part of it, beyond the Kickstarter. I bet there are people who would even donate $5 just to get into such a file on what might be a popular project :-) (sad but true!)
My real thinking behind this is because I might be including this in JavaScript Weekly next week. And if I do, I think it would be awesome if people felt motivated enough to throw you some money.