I rode QE Park over Christmas - there wasn't a height restriction to get in (which was lucky as I had the bike on the roof and forgot to remember to check for one)
As I recall, there are two trails and I did the "advanced" one. It started out with a sharp little uphill, then onto a grassy road which was a little disappointing (and very, very gloopy!). Turns out this was because of forestry work around where the "proper" trail goes.
Once over that disappointing section, the trail itself was pretty nice. Some nice up and down bits, nothing overly taxing, mainly single track but with room to pass people if they were there (they weren't - it was 4pm on Boxing Day I think!)
The verdict? Worth a visit. Good location for a retro-meet as there's a coffee shop, car park and the trail is short enough for people of different paces to do as many / few laps as they want. If you want an all day ride, there's better to be had but it's great for a social.