You can of course have a furniture repair business add material and refinish. Or you can add a center accent piece of tile, or wood inlay. If you're going from a narrow rectangle to a square, you would need to disassemble the table anyway, might as well do something fun with it.

Wax is good on a dining table as easy to apply a bit more in the event of cup rings etc.

If it is a casual buffet type meal you don't need to go over board on the dinner table. I would suggest a lovely table runner a pose of fresh flowers (not high so that you block peoples view across the table). Some lovely place mats, standard silverware and glasses all set out and a couple of very simple candle sticks - I also love the idea of the mini Led Fairy lights but maybe around the room (perhaps a mirror if you have one in the room). If you have napkin rings or can make lovely napkins shapes out of origami, that adds a little bit of class and perhaps a small chocolate at each place setting. Don't go over board. After all it is the company (and the food) that should be the star of the night and you need to relax as well. Not every decorative piece needs to be on the table.

I think you're better off lurking the professional's page for this kind of job!