Ideas for day out with small-ish children in East Midlands?

[Clary]

Has anyone got any great ideas? We have an unexpected day together tomorrow (Sat) as no football.
We really need somewhere no more than 1hr's drive from Derby that would be weather proof and suitable for 6.5yo ds1 and 4yo dd, and not tooooo boring for 2.5yo ds2.
Has anyone been, for example, to the space centre at Leicester? Is that any good or would it be a bit old for them?
TIA

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Thanks Orinoco, good ideas.
We have been to White Post but it is quite a lot of outdoor and it's supposed to be cold tomorrow!
I was wondering about Twin Lakes too, could be a contender (just trying to unravel the website!)

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I haven't been personally but my sister really rates Conkers. What about the railway at Ripley or Waterworld in Stoke. A trip to Matlock Bath (although a bit tacky there is quite a bit to do) ie hologram gallery, aquarium,caves, cable cars, Gullivers Kingdom etc

Clary have you looked at localkids

If the weather is nice Gulliver's Kingdom (children's theme park) is great for children. But as it is mainly outside it needs to be mainly dry.

Snibston Discovery Park has a reasonable amount of indoors stuff as it is going to be cold I think! nice place and you caneat your own food there which is always appealing.
My other top choice is The Tramway museum at Crich - you can ride up and down on the trams as much as you want, there is a small indoor play area and a couple of places to eat indoors. Our kids love it and it is very relaxed.. but wrap up warm as some of the trams are exposed.
Twin Lakes is great, and there is a bit inside- your will be too little for the big people's play area.
what about the Midland Railway centre at Ripley?
Perosnally don't rate the space centre and Conkers is better for a warmer day.

I will back up twinlakes, although it is even better in the summer.

twinlakes is fab! The indoor play area is huge and quite adventerous. There is a massive wavy slide.

american adventure have open a new indoor adventure land

Thanks for all these folks!
Actually I think Gullivers is closed in Jan...
I think we are goign for Snibston as another (RL!) friend has recommended it.
I love Conkers too but agree better for warmer day.
Crich tramway is good too, had forgotten about that, must go back there soon!