As you said,I guess the following commands can help you out:
ssh-keygen -t dsa (to generate the dsa keys in server2)
ssh-copy-id -i /home/user/.ssh/id_dsa.pub server1 (to deploy the public key to server1)
1. Generate the keys for both the users("carl" and "cindy")
2. copy their public keys to the server1 using ssh-copy-id as..
[carl@carlws ~]$ssh-copy-id tim@server1
[cindy@cindyws ~]$ssh-copy-id tim@server1
I'm not sure,but try ...it may work.
you can use a passphrase too.