Hi, we always go mid summer, so weather is usually fairly warm here. I often wear crops, with a light fleece/cardigan. DH always goes in zip off trousers - as soon as we get there, he just zips the bottoms off!
It does often get chilly on the plane (more so, on the return journey) - but seems daft taking too many fleeces/cardigans etc when you're going to 90 degree heat! I find jeans too thick for mid summer, so tend to go for linen or light cotton.
The kids have always gone in shorts/crops, again with a couple of layers, just for the plane.
Have a great time!