I’m looking for ghost stories appropriate for kids 7, 9 and 10 years old. Nothing spine-chilling or grisly, but enough to keep them entertained and maybe a little spooked without nightmares.
A quick search at Amazon.com got me this link.
There is a series of ghost story collections for children, retold by Robert D. San Souci, starting with Short & Shivery: Thirty Chilling Tales, followed by More Short & Shivery.
The stories are short, sometimes just three pages long, so you can tell several of them to your young audience.
Would you like to borrow my fog machine? 
I read this when I was a kid and LOVED it.
My teacher would read to us from these books if we had been good that day.
I loved them!
Some fun ideas in this thread:
Halloween story ideas for a bunch of 4-5 year olds
You can just expand or add more scary details to these tales.
Why don’t you want to give them nightmares?
Tell them the story of what happened to the missing 8 year old.
Do you think “The Monkey’s Paw” is too much for your average seven-year old?
Look at some of the vocabulary in the first paragraph alone: parlor, possessed, radical, perils, provoked, placidly, hark, amiably, desirous, surveying.
OK, how about for someone who’s 37? 
I had good luck with taily po