The number of methods you choose to do a redirect isn't really relevant since once a redirect is sent to the browser it instantly does it and never sees another redirect. What does matter is that all of the redirects are 301 redirects. If they are anything but a 301 redirect then you will have issues with your rankings.
301 redirects are not a perfect solution but they a lot better then nothing. Not only will your users find your new URLs without fail but so will the search engines. Plus they will make a correlation between the new content and the old content, and in the case of Google, pass along any PR and any other page specific factors, as well as keep the rankings for those pages.
Keep in mind that 301 redirects aren't perfect. You will see a temporary drop in your rankings while Google makes the adjustment on their end. They also recommend going out and contacting anyone who is linking to your old content and ask them to update their links to your new URLs as there will be some PR loss from those links.