Just remembered Lordenshaws.
http://www.themodernantiquarian.com/browse.php?site_id=2917
It's about an hour north of Newcastle.

It has a very rocky carpark :-( but once this is negotiated there is a decent turf path up a not-too-steep slope to the main rock.
Not sure of your team's fitness but it's about 500 yards uphill to the rock. The main hillfort may be achievable, it's about another 3-400 yds.

[Last time I was there I was assessing it for access by a relative with a bad heart & new hip and I reckoned if she could walk around shopping in town she could manage this with maybe a few pauses for breath. she ain't been yet]

.o0O0o.