Just after some advice as a I have no experience with group bookings on BA.

I am looking to make a booking from LONDON to SPAIN for a family trip. This will be for 8 adults and 5 kids & 1 infant.

Am I better booking as one Group Booking by contacting BA or splitting the group in two and making two online bookings?
What are the benefits / disadvantages of doing a group booking?
Clearly I am not going to get the whole group into the lounge on my silver status, but are other status benefits available on group bookings? (Eg. Seat reservations).
Are BA Holidays available as a group booking (I.e. Flight and some cars) and would this be eligible for the current double tier point offer?

Thanks in advance for any insight or thoughts.