Welcome, it depends on the ages of your children. There is so much that can be learned. You could focus on a number of themes. For nickels you could look for the 2005D Buffalo and perhaps find the one with the die crack that makes it look like it has a spear in it. Or the 2004 Peace nickel that has a double die on the obverse. If you get penny rolls, you can start by sorting them by date. I have found that I average 15 pre-1982 coins per roll. If you get a roll that breaks that average pay close attention. Sometimes rolls get turned in after someone passes away and the kids are cleaning up. I have found rolls loaded with good coins that someone else collected and the kids turned in. You might want to get a USB scope that you can look at the coins on your computer.
The quest to get rich with coin discovery is possible if you can teach that it is not the monetary reward of a valuable coin found as much as in the life long lesson of learning to observe. The truly great in any profession are masters of the details. You want them to see things others miss. Happy hunting.