Usually it is best to book with the group department. You make a deposit and don't have to give names or final payment until 30 days prior to trip (60 days if international). However one consideration is, if you book on jetblue.com they will honor lower far if the fare goes down between now and the time you travel and you call and request it. They refund the difference to a travel bank to be used on jetblue within the next 12 months. At present the group department is no longer doing that. The schedule extension is available now.