I agree with Hillia.
In our experience, there is often laughter at meals following funerals. A toast will usually be offered to her/his memory and people will recount happy memories.
'Remember when Uncle Joe had that blue motorcycle and gave us rides around the block in the side-car?'. 'Ooh, wow! that was fun!!!'
'Remember how Aunt Katie used to play the piano after Christmas Dinner?' 'She didn't play very well but we all had a good time. I'd Love to hear her play just once more'.
You know the sort of thing.
However, the kids running wild and damaging the restaurant is not acceptable. The older children
are often the leaders and, if they're allowed to do it, the younger ones will follow. Once it starts, wild behavior will escalate until it reaches the level in the OP. Parents have to step in at the first instance and quell the rebellion.
If the later party is still being considered, great care should be taken with the guest list. It would be a shame if the Anniversary party had to be cancelled. Still, it might be a good idea to give a stern heads-up to the family. People love to see their Great-Grand-Children. They just don't want to see them wreck the place.
We had an experience like this several years ago and NEVER want to repeat it.