We went Sunday and Monday, stayed in the Holiday Inn in Slough.
We managed to get there for 9.30 the first day which was useful. Our children are 8 and 4, and we did some of the big rides, but they were not hugely keen to be honest, my daughter didn't really enjoy the Dragon roller coaster and my son got upset when he was hit by quite a powerful jet of water on the Viking boat ride.
DS did love the Star Wars experience and went both days.
They both liked the smaller splashpark and the playpark next to it in Duploland, also the pirate playpark.
The second day was totally heaving, I think a lot of schools had inset days, and it was very sunny.
We got there a bit later, 11am, having packed up and driven in. We spent too much time having a comfy hotel family breakfast, I think next time I would ask to pack up some rolls with sausages and pains au chocolat so we could finish breakfast in the car on the way.
I did have snacks aplenty, including lots of fruit, we took 2 big M and S coolbags with us. I replenished from Tesco in Slough for ham and berries for the picnic on the second day. It was great having picnics outside, while watching shows etc. We split up both afternoons and arranged to meet in Miniland which was interesting from a model building 8 yo POV and also green and pleasant.
We did get ice creams, the queues for those and the prices made me relieved we were sorted otherwise. We still have a buggy for my daughter, we could have done with a 2 litre bottle of water or 2 in the bottom, we drank all the water we came with quite quickly.
I did wonder about Qbots but my children did not seem that enthused by some of the big rides. I felt a bit irritated by the apparent queue-jumping and thought that I didn't really want to queue jump myself either.
The second busier days, we spent a lot of time in the sunshine watching shows, the pirate one, the Lego friends one, the Celebration tea time one and a puppet show. There were no queues for these!
I was really pleased they stayed open an extra hour on the Monday to help with the extra demand. We had a look round the shop after, we did 'nt leave till nearly 7 and there were not too many problems with queues by then.
Mumsnet info was vv useful.