We went there for our hols back in June. Didn't get great weather but had a brilliant time.
Best place we took our DS to (aged 20m at the time) was Whitehouse farm centre in Morpeth. We spent a full day there - the weather wasn't brilliant but there are mixture of things to see outside and inside. They have a wee play park, tractors to play on, go karts (for all ages , bouncy castles, trampolines , lots of animals etc. It was really fab and very reasonable too. Plus they have a barn where you can buy food in and a picnic barn if you take your own. I thought that was a really good idea so that you can shelter if the weather isn't so great.