some dogs are good with munchkins, some are not. in general, Greyhounds are real gentle couch potatoes -- they are not "high rev".
we don't have any munchkins, but from what I've observed, if a greyhound is feeling "annoyed" by someone (adult or kid) they just get up and walk away.
a good greyhound rescue organization will try to match up a family with a greyhound based on the family's life style and situation. They will ask if you have kids (how old they are) and other animals in the house etc. They are interested in finding FOREVER homes for the greyhounds and will make an effort to make the best match possible.
The greyhound org I work with - the majority of "new" dogs coming in are placed with foster families for a time. This gives the dog time to adjust/learn what it is like to be in a home, learn things like how to walk up/down stairs, what sliding glass doors are about and gives time to evaluate the personality of the dog (likes/dislikes, do they interact well with kids/other critters etc.) On average a dog is usually in a foster home 4-8 weeks before actually being adopted.
link to Rainbow's End Greyhound Rescue. Sweet Valley, PA (near Wilkes-Barre --->
http://reghr0.tripod.com/