You're probably better off selling it. Your top capital gain rate is probably 15%, whereas the kiddie tax is 20% on most of a $50K gain (see https://www.marketwatch.com/story/new-tax-law-makes-dreaded-kiddie-tax-more-expensive-2018-09-24).
But, the only way to be sure is to prepare returns both ways and compare. It depends on the exact numbers. Your effective tax rate is not as important as your taxable income. You don't reach the 20% capital gain rate until your taxable income is over $400K (see https://www.marketwatch.com/story/your-simple-guide-to-the-new-capital-gains-tax-rates-2018-04-16).
