Here's an easy way teachers can help us follow up on visiting kids:
Have the visiting kid write their mailing address on an envelope. Then after class fill that envelope with three things and mail it:
(1) A fun "thank you" card for the child.
(2) A coupon for a free scoop of local ice cream.
(3) A flyer for the parents.
Don't' forget to give a copy of the address to the church office!
Children's ministry mag has this free printable postcard you can use to get started. The image could be your "fun thank you card." Before you use it, edit the pdf/image to add your church's logo, website and class and worship times.
[Yes, kids still love to get "real" mail. Adults are jaded with real mail because of all the junk and bills, but who doesn't love to get a handwritten note in the mail!]