AWS CloudFormation: How to get subnet list from VPC?

In CloudFormation, I'm creating a VPC, two EC2 instances, and an Elasticache in front of them. In the template, I'm trying to add the elasticache to the vpc. The problem's happening in creating the AWS::Elasticache::SubnetGroup

    "CacheSubnetGroup" : {
      "Type" : "AWS::ElastiCache::SubnetGroup",
      "Properties" : {
        "Description" : "Subnets available for the ElastiCache Cluster",
        "SubnetIds" : [ ... ]
      }
    },

I do not want to ask the user to input the subnet list as suggested here because I'm assuming the user doesn't know what a subnet is. Is there any function similar to { "Fn::GetAtt" : ["myVpc", "SubnetList"] }?