It's not at all a matter of whether the 4Runner is capable of driving on them. It's an ecological matter. Below is just a small blurb about why you shouldn't and that'll be the last I mention of it.
Sand dunes need to be protected so they can continue to protect coastal communities from coastal erosion and flooding and so the natural character of the coast is preserved for future generations.
Dunes are formed when dry sand is blown up the beach and trapped by native sand binding plants. The plants then grow through the trapped sand increasing the height of the dune and becoming a natural barrier between the land and the sea. The greater the width of the dunes, the greater the reservoir of sand available to provide protection from storm waves.
Any activity that damages these important sand binding plants can stop the dunes from rebuilding and can lead to increased erosion.
Driving over sand dune plants can destroy them and lower their growth rates by breaking off stems, crushing seedlings and damaging underground roots.
Vehicles also compact the sand and soils which changes the conditions needed for sand binding grasses to grow.
The loss of plant cover, as well as the physical changes to the sands and soils, makes dunes more vulnerable to wind erosion and 'blow-outs' - where the dune gives way and sand is blown inland. Driving on dunes can also change the profile or shape of the dunes, creating wind funnels and making the dunes more vulnerable to erosion during storm events.
OP, please don't be that guy.
