In this paper, we investigate optimal boundary control problems for Cahn-Hilliard variational inequalities with a dynamic boundary condition involving double obstacle potentials and the Laplace-Beltrami operator. The cost functional is of standard tracking type, and box constraints for the controls are prescribed. We prove existence of optimal controls and derive first-order necessary conditions of optimality. The general strategy, which follows the lines of the recent approach by Colli, Farshbaf-Shaker, and Sprekels [Appl. Math. Optim., 71 (2015), pp. 1-24] to the (simpler) Allen-Cahn case, is the following: we use the results that were recently established by Colli, Gilardi, and Sprekels [Appl. Math. Optim., Online First DOI: 10.1007/s00245-015-9299-z, 2015] for the case of (differentiable) logarithmic potentials and perform a so-called deep quench limit. Using compactness and monotonicity arguments, it is shown that this strategy leads to the desired first-order necessary optimality conditions for the case of (nondifferentiable) double obstacle potentials.