In terms of negotiation, it is important to know whether your targeted schools budge at all on scholarships. I get the impression that the Dulwich schools are less likely to, but the Croydon and GDST schools do.
At this stage you are trying to pick up any information possible about how your child has done, and in particular where they sit in the cohort. Whilst certain schools want to know that they are your preferred choice, there is no harm in indicating that you may have other offers. Co curricular all come into the mix too, and there is no harm in continuing to firm up any skills here (eg the next music grade, music festival, gala etc).
I think that you also need to think about your child, and how they are likely to develop over the next seven years, and what the scholarship may or may not mean to them. The co curricular scholarships are sponsored by those departments, and the departments may expect their pound of flesh. Do make sure that your grade 5 violin player really, really wants to be in the choir, and not in the swim squad! The two activities may not be compatible. [well, they may, but the point is you can't do everything, but there will be some things you have to do.]
The largest awards, and where there is the most scope, are the academic awards, and as far as possible you want to know where your child has been ranked.
I think it would be unreasonable to assume that scholarships are there for anyone who wants one or asks for one. They are awarded on performance, and your child has to be able to sustain their relative performance. But it is fair to say that there is some movement on offers and scholarships post 14 February.