If you cannot walk, the little overlook at the visitor center would probably be as close as you can get in a wheelchair. If you can walk, but not far or to the top, there is plenty of flat areas in and around the dunes you could enjoy, but no path to the top. If someone in a wheelchair wants to roll up to a high point for a look around, the Wright Brothers Memorial has nice view from the top. I pushed my brother up there once, we were both completely worn out, but it was worth it.
Yes there is an overlook near the visitor center that goes out into part of the park.
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