Not familiar with the specific model, but have you checked if memory is upgradeable? Is it a white Macbook? The one I just researched, 2.26 unibody, can be upgraded to 8GB for $99. RAM, next to an SSD are the absolute best upgrades for any computer.
I tend to think Mavericks will work just fine, but extra RAM wouldn't hurt.
It meets the requirements, so you should be fine. I would invest in the RAM at some point. It's relatively cheap compared to the performance you'll get. Macsales.com offers fair prices and are very good about warranty on RAM. I had RAM go bad and they replaced with no questions asked. Fast, great service. I'd buy from there again if I needed more RAM.