We were there spring 2018 and observed Happily Ever After (HEA) from three spots, Main Street USA, the Contemporary California Grill Observation Platform (South, closer to Wilderness Lodge end), and the Contemporary Concourse (4th floor) deck. To us, in our opinion, while all three work, the optimum is obviously in park itself. 2nd would be California Grill (all fireworks and music, overall entire atmosphere and surroundings) with less visual detail on the projections. 3rd would be the Concourse (nearly all the fireworks and all the music, virtually no visual detail on the projections).
So, to answer the original question, yes, HEA is observable from the Contemporary Resort, but, in our opinion, not to the same extent as possible while in the Magic Kingdom.