here is my dilemma, cooking for a group of 30
group is meeting in a park where I cant bring a pit or even a grill
so i need to cook and then transport the food

thankfully the food is simple   hamburgers, link, boudain stuff like that

I transport briskets in a dedicated cooler all the time no problem
large mass in a preheated cooler keeps it at temp

so how do I keep a bunch of smaller mass items warm?
the cooler will keep them warm, but the minute they go on a table they start losing heat
considered the gel fueled serving tray setups but I dont want to dry out the hamburgers anymore than possible

I know this might sound dumb and maybe I am overthinking this
but the last thing I want to do is serve cold food

You can probably still use the gel fuel serving setups, just put a container in that won't melt and put water in it. That will create moisture so the burgers won't dry out.

I'm thinking the wire chafing stands are going to be your best bet.
Because they act like steam table they work very well for keeping things hot without drying them out.

The chafing dish set up is your cheapest bet. If you want to spend the money you can get a Cambro or Carlisle insulated box. We use them and they work great. Put a pan of the hottest water you can in the bottom tray and then the food up top and there is still steam coming out of this thing after an hour being shut down. Of course you'll probably have no way to get water that hot at the site you're going to but it does a good job keeping the meats hot and moist leading up to travel time (can't really travel with the water pan).

well I went with the chafing stand
BUT the person responsible for getting the chafing stand didnt get there until 15 minutes after it started
I transported in a prewarmed cooler like I do my briskets

worked pretty good, 90% of the food was gone before it even had a chance to cool off

When we have to keep hamburgers warm without drying out, we pour some beef broth into the bottom of the warming tray. These are for boy scout events and it does impact the flavor but it works.