Yes, they do have VK Child Vouchers. Not sure where you can get them as Hotwire, thanks to MYW, is no longer selling them. Sure, there is Ebay but the mark up there is usually signficant. So you might have a problem locating - not sure.
I would NOT use a VK lunch voucher for a child. We used VK vouchers once and selected Cinderella's (as I was heart broken we were unable to get in for breakfast). While I found it to be a bargain for myself and my husband, they did offer a child's meal at Cindys that would have been fine for our then 4 year old and that child's meal was only $6 - far less than the cost of the voucher. We ended up having left over food which we had boxed and she did eat later.
I would look at allears.net and see if the restaurant you are interested in has a kid's meal. $30 for a kid seems steep to me....