Activity for ARIANA

Is it okay to choose black style invitations if It is at an upscale venue, three hours open bar, valet parking but no band just a DJ? I will NOT put black tie on invitation nor do I want it to be we just really like these invitations.

I am wondering if it is necessary to hire both a cantor to sing and a pianist for the ceremony or if just the pianist is ok. Anyone been to or know if it is worth getting both?