If you're going to have 3 Rorate Masses, I encourage you to look beyond Jubilate Deo. (The name has always bothered me, since parts of this composite Mass are from the Requiem.) Maybe use Mass XVII?
Additionally, have you considered singing the proper chants of the Mass? You could easily sing the rorate caeli during communion, sing all of the propers from either something like Simple English Propers or the Graduale Romanum, and have a full sung Mass that the church really wants!
Actually since its a weekday during Lent, Mass XVIII would be most appropriate. But use Kyrie XVIII which is not part of the Iubilate Deo - and maybe a polyphonic ordinary for the final Mass with the mixed choir.
If these Masses are in the EF/classical Rite the Mass, one of the Masses of Our Lady would be nice (IX or X) as the Gloria is sung. The Rorate Mass can only take place if there is not a 3rd Class feast or greater which can be tricky in Advent, without the express permission of the Ordinary.
To participate in the discussions on Catholic church music, sign in or register as a forum member, The forum is a project of the Church Music Association of America.