MIL won't take my daughter to Legoland

[MissKatyKat]

Okay I'm really annoyed about this so would appreciate thoughts from others.

My MIL is quite a young grandmother and has two friends with young children, similar age to my daughter who is nearly 11 months old, so they socialise together at a baby group. That's fine with me, I do other things with my daughter and it's nice that she has a good social life.
A few weeks ago MIL told me they were planning to go to Legoland and was it okay for her to take my daughter? I also have a new baby son so I have no problem with my daughter being taken on a day out that we can't really do ourselves with the baby just yet.

Anyway, my daughter has had some ongoing stomach problems for the past few months which had been dismissed as "just one of those things" until recently. She has now had a small procedure to correct things earlier this week and came out of hospital today. She is recovering well and has been really good about the whole thing, so I feel she deserves this day out more than ever. However, talking to MIL this morning, she just drops it into the conversation that she won't be taking my daughter to Legoland now (in 2 weeks time) because she doesn't think it's a good idea after the operation, although she is still going with her two friends and their children who are aged 18 months and 2 years. My daughter's stomach problem caused her to suffer badly with wind and sometimes get diarrhoea, which I appreciate isn't pleasant to deal with, but the procedure she has just had is meant to stop this from happening again, although because she's just had an operation her stomach will take a bit of time to settle, but not anywhere near as bad as it has been, and my MIL has looked after her many times when she's had one of these episodes.

So her argument now is:
"The other two children are walking so she'll have to be in her pushchair to keep up and I don't want to drag a pushchair all round Legoland".
And
"It's not really fair on the other two children if I bring a windy, smelly baby along who can't go on any of the rides".
But it was her SUGGESTION to take my daughter to Legoland (and there's plenty of rides she can go on), and her condition is now BETTER than it was when she made that suggestion.

So AIBU or is my MIL being totally ridiculous?

@TeddybearBaby and @MoominKitty thank you! I'm so glad somebody gets it! That's literally all there was to this and all I wanted was a bit of perspective which I now have :)
@SandyY2K thank you for the good luck, but with respect my personal life has absolutely nothing to do with this thread and my relationship is in a perfectly stable condition. I don't know why a previous post felt it necessary to bring any of that up, apart to encourage gossip.
Just an update to make things more complicated, MIL now says she can probably take my daughter if I make her a packed lunch. This is what she's like, you never quite know where you are with her. I've said not to worry as having thought about it properly and spoken to others I don't think it's a good idea. Yes, I know this thread has now gone full circle, and yes, I know I was totally wrong from the start in agreeing my daughter could go. I won't make the same mistake again and I apologise for how this thread has gone.

OP I think it is hilarious, imagine your MIL struggling round legoland up hill, down dale with big crowds. She will be cursing the day she ever thought of agreeing to it, as will the others, one of the seven circles of hell in the school holidays.