Hiya!
We had a bubble machine at our wedding - we could only have it operating outside though because our DJ warned us that a bubble machine near the dance floor may cause a hazard.
Everybody love it and it looked absolutely fantastic in the photos. Regarding bubbles staining your dress - I don't think my dress was stained but I made sure that I didn't stand in the main flow of the bubbles.
We bought our bubble machine from the Gadget Shop - it's been a brilliant investment because we have since used it at our house-warming party and plan to again at our Halloween party later this year.
I hope this help.
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Beeny