I don’t have any memory of anything specific a groom’s parents did at a wedding that stand out. I actually don’t remember anything a bride’s parents have done that stand out. Except to stay one wedding was basically a weekend of events, and the RSVP went to the bride’s parents, so the extravagance, the money spent by the bride’s parents, was hard to ignore. But, I’m prerty sure you’re not talking about money.
The day is for the bride and groom to stand out. Although, at my own wedding I cared most about everyone else having a good time. I didn’t break up the reception with a lot of attention getting things that stopped the eating and dancing. My dad and my husband’s dad did the blessing over the bread, and my dad gave a toast (because we decided not to ask my husband’s brother who was technically the best man). I’m very glad it was my dad who did the toast. If my FIL had asked to do one, I would have been happy with that too. In fact, in my video to my SHOCK my inlaws are very animated and my MIL is smiling and talking (almost every photo she frowning) and they say how they wish us every happiness, etc. if I had seen that during my wedding as a toast I would have been so happy. My SIL in the video said the line, “I hope everything in your lives is as beautiful as tonight” something like that.
Some ideas:
You could ask to do a toast. Say you welcome her into the family, or your confidence in their ability to walk through life together, or something along those lines.
Or, you could host the rehearsal dinner, or a brunch the day after.
If they aren’t planning on a videographer, maybe offer to pay for one. I didn’t want to spend the money, but my husband did, and I’m so glad we did. The guests might not perceive it as something special the groom’s parents did, but I think the bride and groom will.