Show some photographs (normally childhood or embarrassing ones, or often a combination of the two) blown up to a large size so they can be held up for all the audience to see.
Use some joke shop kit if you’re struggling and after a really cheap laugh. Fake hands, whoopy cushions or pink love cuffs that you have tucked in your inside pocket which only become shown when you reach in for your speech for example.
If you are technically advanced, put together a mock-up newspaper or magazine front cover with the Bride & Groom featured on the front and display to the guests via an overhead projector.
Prior to getting stuck in to the speech, pass items out to the guests (or offer to do so) such as packets of tissues for their 'iminent laughter/tears'.
Granted, not all of the props will be suitable for use during that upper class, formal gig you are speaking at, but I think you get the gist.
