Thinking of taking the kids there on Sunday, but not sure if it's too old for them. They're 5 and 4, and from the looks of the website it seems to be aimed at older kids. Has anyone been, and if so, do you think little ones would like it?

Went their a few year ago. Thought it was really good. My dds are now 10 and 6 so the younger one was defiantly under 5. They had a really big imagination play area where you could pick up the phone in the drs and call the cake shop or the garage. Also had a water-play section so take spare tops just encase. I thought the whole thing was very good lots of interaction. Look out for cards to collect stamps on.
There was an area for eating sandwiches which I wished we had done the cafe outside wasn't that good (this was a few year ago so may be better now)
We will be going back at some point as I thought it was a good day, we like in Bristol

I was going to say take a spare t-shirt, as well! My DCs used to love the imaginative play area, would have spent hours in there; when we first moved to the area they were 5 and 6 and we bought an annual pass because they enjoyed it so much, great way to spend a rainy day.
They also liked the recycling area, and again spent ages there sorting the 'rubbish';not sure why it appealed so much!
We used to take a picnic, there are a couple of different seating areas, cafe is ok but coffee is awful; however you can pop out to the cafe near the entrance doors and then bring their starbucks coffee back in.