Deck idea for seasonal site.

I would place these on the ground. Get them level and place them about 6' on center.
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You can slide 4X6 beams through the brackets without securing them. nothing should move.

What ever you do, get the parks approval before you spend any money.

Over the years we've had several "seasonal" sites and each one had different rules pertaining to what you could and could not build. If it were me, I would talk to the office and get a copy of the latest rules. Then walk around taking pictures of what you like. Don't be surprised if what you like can no longer be built. The building rules might of changed over time and what you really like might not conform to current standards.

We used to like wooden decks that are level with RV. Having the deck raised is great for some storage under deck if done right. But found that they get slippery in winter time. Last one we put in was patio blocks at ground level with a wooded railing around attached to a canopy.

Also be aware that some people hide behind the ADA rules to enlarge their deck.

link with lots of ideas. https://www.google.com/search?q=rv+decks&biw=1301&bih=589&source=lnms&tbm=isch&sa=X&sqi=2&ved=0ahUKEwjztI6X7tjRAhVW0WMKHSzYDIcQ_AUIBygC

just use the concrete blocks as shown in the lower right of the picture.

2x6's are plenty heavy, we had a 8 by 20 deck at our seasonal (now it's 12 by 28 and has a roof) but it was NEVER going to blow away.

green treated 2x4, 8 feet, is 13 lbs by itself. Multiple that by x number of boards in a deck, I doubt it's going to move much.

edit: read the pounds wrong, 8 feet green treated is over 20 lbs