Group Membership - Allow Group Admin to Specify Type to group member

We may be a bit unusual in the way we use Membership Pro. We have 3 basic types of membership, Adult, Child and Family. The 1st are individual memberships, no problem. The 3rd type Family we have a number of plans.
A1C1 ( one adult + one child)
A1C2 (one adult + 2 Children
A1C3
A1C4
A2C1 (two adults + 1 child)
A2C2
A2C3
A2C4
When someone takes out a A1C1 They can add 1 group member (child) A1C2 can add 2 group members, A2C4 can add 5 group members. This is all fine, but what we can't do automatically is differentiate between Adult and Child group members. The reason we want to do this is we also use Events Booking. In events booking we have Family Events, Adult only events and Children only Events.
So we want that only the Group Admin can book Family Events, Adult can only book Adult Events and Children can only book Children events. To do this we use Joomla Groups 
So for example, A1C1 Holder gets a A1C1 Joomla group and they are the only ones who can book a Family Event. We make all Adult members A1 and Child members C1
When the Group Admin adds a group member they can't specify the type of member, So the group member gets allocated as say A1C1 or A2C1 depending on the subscription plan of the Group Admin.
What we would like is for the Group Admin to be able to add group members based on their type.  So, for instance, a A2C1 could add 1 adult group member (A1) and 1 child group member(C2)  and A2C2, could add 1 adult group member (A1) and 2 child group members ( C1).
At the moment what we have to do when a user adds group members we go back through and allocate the correct group ie A1 or C1
I can't see anywhere in Membership Pro we could do this automatically
Any ideas?
I have added some screen shots which may help with explanation of my issue