Introducing avoidance tactics of a tiny ginger

I am probably a terrible mother. I am not able to calmly talk in a singsong voice when my children misbehave. I don't nicely ask them to stop and explain that their behavior is "upsetting mummy" like I'm sure good mothers do.
I get cross, they get cross, I shout, they scream, we both end up red in the face, people stare and I try to pretend that I'm not bothered. It never looks convincing.

Take a recent trip to a play Cafe with Daughter Number One, Two and a very pregnant family friend.
The play area itself consists of a three tier play frame with the usual tubes, slides and customary ball pit.
Having allowed D1 to tear around the play area for a good couple of hours whilst we excitedly discuss friends imminent new arrival the time comes for us to leave.

I clearly didn't think this through. Rather than waiting until D1 is somewhere I can grab her I stupidly announce to her that its time to leave whilst she is at the top of the play frame thinking that having had a very generous amount of play time that she will happily agree and trot dutifully down. Nope.

She shouts that its not time to go and that she is staying to play. I immediately demand that she come down in my sternest voice that never fails to get husband jumping to attention. Nothing.

This is the point where I exclaim "right if you wont come down then I will come up there young lady."
Has any full grown adult ever attempted to negotiate a play frame designed for under fives? Needless to say I didn't really get much further than the entrance. On reflection I am glad I saw sense and didn't try any harder to get up there as my behavior was already starting to attract attention and I imagine a mother becoming stuck in the play frame would ruin everyone's afternoon.

I therefore walk back to family friend (who I can tell is trying very hard not to laugh!) and tell her that I'm going to play it cool, pretend we are not leaving and wait for D1 to emerge.
That's when she starts toying with us. She slowly wanders up and down the top tier, waving at us in a very smug "I've outsmarted Mummy" kind of way and basically looks very pleased with herself.
The only way down is a big slide on one side of the frame. She hovers by it for what feels like an age with me trying to look nonchalant and not bothered whilst actually getting more wound up by the minute.

Then she gets really cocky and decides to go down the slide backwards on her front.
I sweep into the play area so fast I accidentally stand on another parents foot but don't care, so desperate am I to save face and regain control from the two year old currently calling the shots.
She is strapped into the pram before she can blink and I can tell the adults are holding back rapturous applause for this very public victory for parents everywhere.
She screams all the way out and I pretend that I'm not bothered. It doesn't look convincing.