Passing Real Estate To Your Kids - How to Structure

My parents (aged 81 and 89) have 3 rental properties that now have sizable equity of approximately 1.5 million. While the equity gain is nice these properties have low cash flow. They'd like to move these assets into cash flowing assets like syndications and apartments to increase cash flow to benefit their children (my sister, brother and myself). What would be the best way to structure this from a tax perspective so they could pass along the cash flow to their children while they are still alive?  Appreciate any feedback.