The problem with online translator is that they are not reliable. To get a perfect translation nothing beats a human. Once you have your translation it's a good idea to find a French person to look at it, making sure the are no errors.
I agree with Iza 100%. I once had to do a fairly lengthy translation (English to French) and I used an online translator... It's no wonder its free! I think for something as specific as a menu, it's important to have it done properly and with the right spelling. It's not as easy as it looks and the online service is sure to butcher it. How much do you have to translate? Might be able to help you out right here..