Since the files are in avi format you could join them all together into one large avi and then a program like winAVI to convert the large file into DVD format. If the combined files are over 2.1 GB then you need to get them down to just below 2 GB as the encoding will make them just about 4.1 which is all that you can put on a single layer dvd (unless you use DVD Shrink to compress them down to all fit on one DVD.
Be aware that some DVD players will not play home burns. The following is a list of those players that I know will play burns:
Apex made before Jan 2004
Also, you need to install the Ace Mega Codec Pack and the divx/xvid codecs as well.
If I can help in anyway just ask.