Here are a couple pics of the table set if it helps at all. I am really not sure what type of wood the veneer is made from. I was told the table was made from hardwood solids with a veneer top. Just wondering if applying polyurethane to the top would be a mistake or not.

A few years ago my "annual project from Hell" was a table the the owner bought, decided she wanted it glossier and applied polyurethane. She called me in and 1/4 of the top had already peeled off. Granted, she had put it on too thick, but the adhesion was the issue, not the thickness.

Most likely, your factory finish table has lacquer on it. Rather than polyurethane, you could apply some brushing lacquer on it, assuming you have good technique.

If in the odd case it has a conversion finish on it, forget it. Nothing will stick to it (last year's project from Hell).

Or you could just wait until it gets tired looking and then strip and refinish with the finish of your choice. No finish is going to really protect against impact enough to dent the wood. You have a few thousandths of an inch of finish there.

Thanks for the response bobsmyuncle :) I have just about decided I might as well use a pad and tablecloth when eating and uncover the top when not in use. Someone else suggested applying a paste wax to the top every 6 months. Any way for me to know whether lacquer or wax is better? I have an 18 inch extension leaf I could test on.

Thanks again for your input.

Another suggestion, one that I've used for over 25 years and also made one for my daughter:
For everyday and expected rough use, I have a slip-on cover made of Formica. When I want to use the wood table top or insert leaves, it easily lifts off and stores away. Any cabinet shop should be able to make one for you.

The VOC rules have driven manufacturers away from straight nitrocellulose lacquer.

Newer furniture may have any one of a number of 'conversion varnishes' applied to get quick drying and a good appearance like lacquer.

Before putting any additional finish on you should try talking to the manufacturer about what finish is already there.
There are usually methods that can be used to put additional layers on, but there may be requirements for extra layers to get good adhesion.

Even some mechanical roughing (light sanding) may not be enough to get a new layer to stick to factory finishes.
Some are very hard and very slick and smooth, with compositions not compatible with commonly available consumer finishes.

Vinyl isolation coats can even be needed. Luckily you can now purchase them and do not have to dissolve vinyl pellets in toluene.

Manufacturer's information and a real pint store should get you what you need.

You can perform some test on the underside with little risk, but should apply the same finish to the top and bottom to minimize warping.