Personally, I prefer the smaller venues such as Vista over the larger such as Costa Mesa (both California sites that I know you have been to -- I've never been to a Games out of the state).

My main reasoning is that I like the athletics to be in the "heart" of the venue rather than stuck out in a remote area. The year we went to Queen Mary was the worst for that (among many other "worsts" of that venue!), with athletics in a small grassy area at the bow of the ship, completely removed from the rest of the event. Costa Mesa and Ventura also seem to isolate the athletics.

Starting with a smallish site such as Vista's does prevent you from growing too much in future. But I'd rather attend a small, well-run Games than an overwhelmingly large event.

We also enjoy the British car clubs that show up at most Games, depending on where you are there are a variety of clubs that could be interested in a display.

Check out your potential site's current concessions (food/drink) as they may have additional restrictions on event-specific food/drink vendors (i.e. the current concessions may have exclusive rights to sell at the site).

Best of luck with whatever you have in mind!