Bollocks, just did a really long post saying where we went and what 'worked' with the children and then accidently wiped it off
Thanks everyone for posting (not sure what happened to OP!), I actually left at 5.45am on the Wednesday you all posted, wanted to get through London before the congestion charge!
We really liked - Pilipalas, Welsh Mountain Zoo, walking to Aber Falls (DD managed to do it without the pushchair, although I had to carry her a bit on the way back) Rhyl Sun Centre (very busy, and a bit pricey)
Liked visiting Llangolen, but the horsedrawn canal boat trip was a waste of money (no views, relaxing for us, boring for the children)
I wouldn't recommend the Deep Mine Ride at the Llechwedd Slate Mines for under 8s (unless they have nerves of steel!) In each cavern through the tour, they start by turning all the lights out! Far, far too dark for my two youngest. I had to carry a crying DD all the way through, and there's no way to cut it short.
Best thing we did though was get an electric hook up for the tent, and take a TV, Freeview box and the PS2. Most of the really heavy rain we got was in the evening, so we just stayed in, watched DVDs and played games.
We had a lovely time despite the weather