We consider how upcoming, prospective large scale structure surveys, measuring galaxy weak lensing, position and peculiar velocity correlations, in tandem with the CMB temperature anisotropies, will constrain dark energy when both the expansion history and growth of structure can be modified, as might arise if cosmic acceleration is due to modifications to GR. We consider an equation of state figure of merit parameter, and analogous figure of merit parameters for modified gravity, to quantify the relative constraints from CMB, galaxy position, lensing, and peculiar velocity observations and their cross correlations, independently and in tandem.