WWYD with a Large Clump of Paper(Cash)

Hey Everyone I, 36 y/o male and my wife 35 y/o female We have about 1.2 M in investable cash (I approx 910k, my wife 280k). I own my own business and my wife works in Healthcare. We are in short term CD's ulimately waiting to purchase more multi family RE, but recently re considering this option. We own a 2 family house, purchased 2020, 3.175% interest rate, our mortgage is 2300, and our tenant upstairs pays $1400 of that, so we are able to live super cheap by house hacking our duplex. We own a 3 family house (purchased July 2024) for 800k, 6.875% interest rate, Downpayment 375k, mortgage 425k. It cash flows enough so 2/3 apartments rented covers the Mortgage/Expenses we bank the income to invest back into the property. Should I buy more RE or make a large deposit i to the S and P 500 or similar fund. We want to be retired by 55 the absolute latest. WWYD?