Should the DJI gound station 3D mapping be able to capture a reasonable ground map thru tall deciduous Oak trees in winter. I expect to process with Pix4D. I would hope to later enhance further the aerial map with a close in set of pics of the house flown maually around at a cpouple differnet altitudes.

I think it would be difficult because the system is photo based.  Multipul images shot at slightly differnent positions are used to calculate common feature and place them in 3D space.  The complexity of the tree branches would make it difficult especially if they move in the wind.  A LIDAR system is usually used to fix ground level through trees.  But its worth a try, on a calm day with lots of overlap between images.