I recently went to a 50th wedding party that was done as an afternoon tea
There were loads of tasty nice sandwiches, several different v tasty mini quiches and some savoury scone/vol au vents served with salad garnish around them if people wanted.
Then there were assorted cakes, choux buns with different icing flavours, malt loaf, scones with jam, brownies, home made cookies and more. Finally there was a big fancy fruit cake that got cut into after the speeches.
It was a really lovely event that didn't need too much intervention and hassle for those hosting. There were plenty of choices and plenty of each so everyone managed to eat their fill.
And as it was a Sunday it meant it didn't finish too late so people were able to get home and have a chance to get ready for the week ahead. It also means it's not quite such a rush to get everything done in the morning.
If you're worried about the catering then it's worth considering!
But other than that the beef carbonade and salmon sound good. My only concern with cooking salmon (or indeed other fish) is that it can make the place smell very fishy which might not be the atmosphere you want to celebrate in! And it can also be pretty grim eating other food which would normally be delicious when there's lots of fishy smell around, it taints the other food. Particularly noticeable if you don't like fish (or maybe I'm biased!) - have memories of mil serving up fish or lasagne when lots of people were ther - and although the lasagne was ok if that was the only thing on offer, it was never good when eaten with the smell emanating from the salmon or trout that she served up alongside it.