Do the insects float on the top??
A few years ago I collected loads of elderberries to make jam. I gave the heads of berries a really good shaking but when I opened the carrier bags in the kitchen they were full of earwigs!
Yuk!! It has put me right off elderflowers and berries!
You must tell us how you get on and what it tastes like. I might give it a go with next years flowers.