Dependences imposed on Subset Sum Problem
This is not a solution, but a reference suggestion.

The problem should be (a special case of the decision version of) the partially-ordered knapsack problem.  For example, you can look at the following paper and the references therein.

S.G. Kolliopoulos and G. Steiner: Partially ordered knapsack and applications to scheduling. Discrete Applied Mathematics 155 (2007) 889-897.  http://dx.doi.org/10.1016/j.dam.2006.08.006