pirate ship ok soft play, but quite a way from M1.
Megacentre might be easier to find - you come off M1 on A57, go to the roundabout at the bottom and then is just off the roundabout. What day are you travelling? Megacentre is not open on Sundays - is also a church.
What about Magna (less than 5 mins off the M1)? If nice weather you can pay just to go into the outside play area without the sciencey bit... The soft play in Meadowhall is really for toddlers so even the 4-y-o might not be allowed in (have a feeling there was a sign last time I was there saying it was for under-3s, but could be wrong).
Magna might be a little scary for 4 yr old, depends how robust - there's loud cracking "electricity" in the lift lobby which can be a bit off-putting. Would be £25 for a family of 3 (presume little one goes free...) although you can use Tesco Clubcard Deal tokens to numb the pain... It's not that easy to talk there either, and the cafe is closed midweek I think, leaving just a coffee cart and a few chairs at the front which has unbelievably slow service.
Sorry if that sounds a bit negative...
Do you want a soft play venue? Junglemania is quite close to the M1, and that has a decent-ish cafe.. Jungle mania
If you know you've definitely got good weather (ie you're 5 mins away ) and want somewhere outdoors, how about this Yorkshire Sculpture Park? It's just off J.37, and has a lovely cafe, and lots (and lots) and space to run around outside. Not sure how buggy friendly it is though - but I'm sure others on here would know.
Hi.. No, I agree with you Vicky about the inside bit of Magna. Took my dds when they were 7 and 5 and the 5-y-o was a bit freaked (though she's easily freaked!). But if the weather is good then the outside bit is a lot of fun.
YSP is further from Sheffield (half an hour or so?) but there are buggy-friendly routes (i.e. there are steps and - further out into the park - bits that might be muddy, but you can avoid them and stay on the main/flat paths). Cheaper too, as you just pay to park (can't remember if it's £2 or £3...).
Personally I wouldn't go to Meadowhell, but it depends how much you like big shopping centres, I suppose!
I was trying to think laterally for somewhere very easy to get to from motorway. Agree Meadowhell can be busy, but just so easy to get to and has plenty of loos and cafes to suit most tastes. I try to avoid it I have to admit!
Magna is great but for older children - is expensive I agree. Botanical Gardens lovely, but a nightmare to direct to, and parking dreadful at certain times of the day midweek - school chucking out time in particular.