Oldest laptop to have App Store
The first appearance of the Mac App Store was 10.6.6 Snow Leopard. 

Any Intel-based Mac will accommodate Snow Leopard. A list of Intel-based Macs can be found here and at Apple's detailed system build versions for Intel Macs. So the original MacBook Pro from February 2006 would be the oldest portable that can run the Mac App Store. 

Depending on which iOS device they have, you might need Lion or even Mountain Lion to run a version of iTunes for some newer devices like the iPad mini or iPhone 5.