Hi BA Mack,
welcome to the Apple (user-to-user) Community.
Re: How to create a video clips of family movies from .vob file on DVD
What to do: If a media file doesn't open or play on your Mac, iPhone, or iPad - Apple Support
Although .vob is new to me, there is a (non-Apple) article online (link below)that seems to give some good tips.
says: "What Is a VOB File? There are multiple uses for VOB files"
https://www.lifewire.com/vob-file-4150712
Eg:
It seems you would be able to open .vob files in the free VLC app, and convert them to formats to use in Mac apps.
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Re: How can I create a short video clip from from the DVD? Can I use iMovie?
Eg: The Photos app lets you change the length of your videos : (or, if more familiar: QuickTime player can too)
How to edit videos on your iPhone, iPad, iPod touch, or Mac - Apple Support
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iMovie would be great for presenting the different short video clips ... ie: so you can easily play just one, or more.
eg ... you can make a menu listing the clips (or join them into one longer movie if you wish) in iMovie:
More info: iMovie User Guide for Mac - Apple Support
All the best :-)