Welcome to the forum!
My program of choice for converting .avi -> DVD is ConvertXtoDVD - but it’s not free. DVDFab won’t do it, to my knowledge.
I know there are free options available, hopefully someone will post them. If you have a version of Nero installed, I believe NeroVision will do the task as well
Edit: However…if you or your family own standalone DVD players which support playback of .avi files, you may just be able to burn them to disc as is.