The £5 charge is well worth paying, without doing so through gritted teeth, the place is well maintained IMO.
There are 2 Xc loops, marked with coloured arrows on trees (either red or blue) the red route is a surprisingly hard work out. Is about 5miles (from memory, visited last month and rode this with a local) with lots of short very steep climbs. Is a very good warm up.
Most fun is had from the dual track and 4x track, suspect a 9yr old would thoroughly enjoy both. Neither are intimadating and all parts of the tracks can be rolled.
There is also a pump track to find, which works well but often has standing water (has been built below ground level so suspect will always suffer with drainage issues).
No north shore remains which use to be a fun part of chicksands, the DH track is pretty mental and beyond me.
Hope this helps.