I've taken absolute beginners to Ski Liberty and Whitetail, which are both under 90 minutes (depending upon where you live in the DC area). Both cater to beginners, especially kids. Check out their websites, which include great webcams so you can check out the snow conditions and crowds.
But I would caution you to think twice about going on Monday. We went to Whitetail on MLK day a few years ago, and they ran out of children's rental skis by 11 am. It was an absolute zoo. Also avoid the Fairfax and Montgomery County teacher conference days and other school holidays. Several years ago, I took my kids to Wisp, which is three hours away in western Maryland. during the two-day Fairfax County teacher workdays, and found that everyone else in Fairfax seemed to have had the same idea.
If you must go on a school holiday or weekend, my advice would be to plan to arrive as soon as the buildings are open, which is generally 30 minutes or so before the lifts start running. The early bird gets the worm, and the first dibs at the rental skis, and I've found that most families just don't have their acts sufficiently together to get there that early. Buy the beginner package, which includes a lesson (which may be great or awful, depending upon how many others are in the group), plan to ski until lunchtime, and then leave. That will be more than enough time for an 8 year old.
If you can swing it, the best way is to take your child out of school on the next good skiing day. There will always be groups of kids there on school trips, but you will avoid most of the crowds, and your child will have a much better first experience, especially if you get there EARLY. Most of the school groups don't seem to show up until after 10 or so.
If you want the most extensive information on DC-area skiing, check out this website.
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