The parks make up a tiny fraction of Federal land holdings. The vast majority is national forest and BLM, which is already leased out to timber, ag, and mining industry in one of the most egregious forms of crony capitalism. And the land is clear cut, strip mined, and over grazed. Government is a terrible steward of the land. The parks should be turned over to the states where they are located and the rest should be auctioned off, but only to individual American citizens and their partnerships - not corporations or non-citizens. Then let the market decide how that land should be used.
Basically, the OP's fear is the usual: he is afraid that HIS values will not prevail in the marketplace and so he wants the government to use force to impose HIS values on others. I might share his values, but do not accept the idea that I can use government to force my values on others. I will express my values by offering to pay to visit parks that remain pristine. If more people are willing to pay more money to visit some crap hole like Disneyland, well then I lose out. Doesn't mean I can start shoving a gun in people's face.
That having been said, this issue is pretty far back on the stove and is not a big seller.