HELP! How do I convert .avi files to play on a dvd player without losing quality or sound?

I don't know if this is the right place to post...I am fairly new to reddit but it seems like you guys are all very smart and very helpful, so here goes. I have a few .avi files on my computer that I would like to burn on a dvd so that my grandfather can watch the shows. I googled this a few times and tried some of the different suggestions, but either 1. the quality was pretty terrible once some kind of conversion happened or 2. the sound disappeared :(

Does anyone have any advice on an easy, quick way to convert/burn these files to a dvd? Free solutions would be preferable...

Thanks so much!