Is this a good time to enter/start investing with robo-advisors? Should we do lump sum (eg $100k cash) or initial $50k cash + DCA $5k/mth over next 10 months?

The short answer is it is never a bad time to start investing, the key is to invest consistently and continue to remain invested for as long as possible to maximise your chances of generating positive returns. This is of course based on the assumption that you invest broadly on an index (e.g S&P500) or a fundamentally strong company.
As for lump sum vs DCA, DCA ensures you remain invested and buy into the dips whenever they happen. DCA is the way to go.