Centre for Life, Hancock Museum, Science Museum or, if they like football, even though they are probably not Newcastle fans, how about a tour of St. James' Park?
I know it's not Newcastle, but how about Belsay Hall if the weather is fine - my children loved the place. They used to like to hide in the cellars in the house, and had a wonderful time in the Quarry Gardens and going round the Castle.
NannyCarol you could have a wander in Jesmond Dene, lots of areas to explore. Try Gibside or Cragside. Brockbushes on the Corbridge roundabout have had all kinds of activities for the children over the Easter holidays, I think there is a surf machine and creepy crawlies this week.
Hello Gillybob - I have been sooo busy and really I shouldn't be on here today either!
I have just found out that there is a small zoo at Kirkley Hall outside Ponteland - it's only open weekends and school holidays, but it sounds worth a visit if you have oung grandchildren. I think it said that they have over 200 animals, but I presume they will be small ones. We're certainly going to take DGS soon.