As top 50 prospects with pretty significant upside, I would definitely hang on to Tatis and Bichette at $3. At worst, they will be trade chips late in the year if you are in contention and want things to trade to teams that are out the running and have begun retooling for 2019.
Bellinger is projected at $25 value in 2018. Would go for well above that at auction due to inflation, so I would keep. At worst, you could definitely find a trade partner at that price.
Correa is projected at $46, so the same situation as Bellinger. Too valuable to let go back to the auction.
Cabrera (assuming Miguel) is projected at $27. If you have the cap space, I would keep and see how he looks the first 6 weeks. Then drop if he continues to struggle with performance or injuries again. Lots of upside if he rebounds.