You need to add a few thing to get both working.
1) you will need a two policy statements
onefor des and 3des
isakmp policy 10 encryption des
isakmp policy 20 encryption 3des
2) You will need two ipsec transform-sets on for des and one for 3des
crypto ipsec transform-set 1 esp-des esp-md5-hmac
crypto ipsec transform-set 2 esp-3des esp-md5-hmac
3) Then on your crypto-map idenify which transform-set to use 1 or 2 -
crypto map vpn 10 set transform-set 1 (des site)
crypto map vpn 20 set transform-set 2 (3des site)
That should be all you need