I took DD and a friend of hers, and DS#2 to a garden centre with a really nice playarea today. DD is 11 and sensible. DS has as much common sense as a bowl of rice-pudding so I decided the stay with him and let DD and her mate go on the zip-wire alone. I left them there with 2 younger children in front of them waiting to have a go. DS and I went off to do our own thing.
About 10mins later I went back and told them we needed to go. "But mum we haven't had a go yet" said DD. At this point there were about 5 LOs with various adults waiting with them. The girls were at the back whilst the parents hussled their kids to the front of the queue as if DD and her friend weren't there.
So I said very loudly " well I think it must be your turn now don't you?".
"Erm mum, we had to wait" a desperately embarrassed look from DD. Which earned me a hard stare and a tut from one mother 
They were being polite and well-behaved and the parents weren't. Why would a parent decide that was OK? 11 yr olds are not adults and they should be treated with consideration too.
A zip wire is not an exclusively toddler thing.
Was quite cross as it happens. It isn't the first time I've seen it. "Big kids" shouldn't be there seems to be the attitude.