Gary - I am going to modify my Harbor Freight bench dog holes.
it comes with metric holes, just shy of 3/4" and as you can tell,
any standard 3/4" peg just won't work. I was going to go with
a 3/4" expansion then I noticed there are no 3/4" rubber stoppers
to be found in my area.
so - I am going to with 7/8" which fits my needs.
I will drill a 7/8" hole in a 1x4 board and use a top bearing router bit
to enlarge the hole - one by one, as there are only a few to do.
for your table, "you could" do the same with a piece of plywood on
the drill press to make the template - then just a couple of screws
(or clamps) will hold it in place while you plunge cut the holes.
if you are going with 3/4" holes, I would use a 1/2" top bearing bit.
don't know what size or type of dogs you will be using.
but, I think I will use 7/8" for my dog holes as I like the rubber stoppers.
and I can use the T-Tracks for any hold-downs I need.
excellent job on your son's table, BTW !!! I like it !!