Ok - I went out and cycled the route yesterday so we shouldn't get lost (more than once or twice). It's about 55km and flat - York flat - apart from the uphill bits (and there's only 3 of them, all short, one of which could be avoided if you were prepared to bypass the ice-cream van at the Spanish Battery at Tynemouth). The route is mainly offroad paths but is entirely tarmac or paved. Apart from 5 minutes at the start and end plus about 3 miles of road in South Shields from the ferry it would all pass the "can an 8 year old ride it safely" test.
1) Start at Newcastle Station
2) Drop down to the river past Life and then head west on the North bank of the Tyne past the Gun Factory to Scotswood Bridge (Hadrian's Cycleway)
3) Cross the bridge and return east past Dunston Staithes to the Swing Bridge (Keelmans Way)
4) Recross the river south to north at the Swing Bridge
5) Head east along Hadrian's Cycleway towards Tynemouth along the Quayside
6) Stop at Cyclehub for coffee and cakes. The cheese scones taste better than they look (I'm told that their appearance was something to do with the repairs part of the cafe being quiet and bike mechanic having baked them...).
7) Continue heading east past Segadunum, Swan Hunters, the Great British Bollard Company, The Wooden Dolly etc. to stop at North Shields Fish Quay for bacon butties at Wight's, fish and chips or beer as your fancy takes you.
8 ) Proceed on as far as the ice cream van at the Spanish Battery (Tynemouth)
9) Double back to the Shields Ferry and cross to South Shields
10) Follow the Keelman's Way west along the South Tyne to the Baltic and the Silver Slug (The Sage)
11) Recross to the north bank over the Millenium Bridge then climb up to the Tyne Bridge. If there's time, there may be the opportunity for a Ping Pong break here - if anyone remembers the bats and balls
12) Cross the Tyne Bridge then swing round to recross the river over the High Level Bridge
13) Finish at Newcastle Station
I'll post a gpx of the final route just as soon as I get round to editing out my multiple attempts at finding a half reasonable route to cross the last 2 bridges. The route is relaxed, suitable for just about any bike and as I said at the start - it's flat. Whilst it goes through what was once a very industrialised area (we pass shipyards, lead works, collieries, docks, a paint factory and the rope works) it is a remarkably green and quiet way.
Oh - one last thing - you'll need £1.50 for the Shields ferry.