You might like to go again 17th and 18th July, if the weather's nice. This is the largest meeting of the year of the Large Model Association - not supersized Sophie Dahls, but model aircraft. The models will be up to around 20ft wingspan, some will be jet powered, and many will be near perfect scale models of WW1 and WW2 aircraft. And they all fly. On both days. There are usually a couple of hundred flying models on display, flown by the UK's best model pilots. Better than me, anyway!
Unfortunately it's not free this time, but if you want a good day out and inspire the kids then it's as near a perfect day as you can get.