Need recommendation for day out with 2 nephews, niece and DD on my own!

[Springchicken]

Am currently child sharing with my SIL due to Easter holidays and we both work.
I have my 2 nephews 11 and 5, niece 10 and DD 8 months for a day next week and am trying to think of something to do.
Swimming is a no no as i can't be responsible for DD and youngest nephew. London on train is a no no as I can?t be responsible for the kids and getting DD on and off trains and tubes in her buggy on my own.
Can anyone suggest anything?????..i am in Luton but don?t mind how far I go, I will be driving.

TIA x

A zoo/farm type place? Sorry don't know the area.

What about Willows farm, just off Junction 22 of M25, not too bad for you, have a look here

Thanks - will have a look

My mum and dd aged 5 went last year and LOVED the willows. We were thinking of going in the holidays. The other place is Knebworth house where there is an adventure playground in the grounds. This is close to Luton (and where I got married!!) Might be better for the older ones who might think the farm too 'babyish' and since they are boys they might like it more

Look here

im in luton im thinking about going to mead farm or whipsnade zoo if you want to join us

Oh bum, just seen that Knebworth isn't open when our holidays are (being in Essex we are not for a couple more weeks) so we won't be going there. It is good though, my neice who is now 12 loves it.

Also one little known fact - I got married there!!