Pick the one moment
Spend 15-20 minutes hereBefore you write a single sentence, pick the one moment about the couple you most want the room to see. Not their love story. Not their relationship in general. One moment, one detail, one image. If you described it accurately, it would tell the room everything else.
The moment can be small. A conversation you had once. A habit one of them has. A photo only you have seen. A line one of them said about the other when they thought you were not paying attention. The smaller and more specific the moment, the more it earns the room. Avoid the obvious picks. "How they met" and "their love story" are setups for cliches because every wedding toast tries to use them. The toasts the room remembers always go smaller and stranger.
If you cannot think of one moment, write down everything the couple does that is not photogenic. The thing that does not photograph well is usually where the real story lives.