You can use mencoder to re-encode the video at a slightly lower resolution to make it fit into a DVD
I use a script I found on the internet to make some videos smaller to put them into my Nokia N95 8GB to play.
Code:
mencoder "$1" -idx -noodml -ofps 24 -vf scale=320:240 -ovc lavc -ffourcc DX50 -srate 44100 -oac mp3lame -lameopts cbr:br=128:mode=0 -o New."$1"
I guess you'd be able to use this little script as a base to modify your file.