Investment Vehicle to Leave for Children

My father is making available some extra money he has to me in order to invest in stocks/real estate. We both have a very long term approach to investing and money, and the end goal is to prepare some assets to be shifted from his name over to me and my sister upon his demise. Hopefully, that will still be at least 30+ years away, but we want to get this setup right from the start.

To clarify, I am not looking for advice/warnings on mixing family and money as I am well aware of many of the pitfalls but I do not think they apply to our situation. This isn't money that is needed for living expenses, and the sole purpose is long term value creation.

What I am looking for is advice on how to structure an investment account/vehicle so that I can manage it with my father, and can be most easily and simply (and perhaps most tax-efficiently) left to me and my sister some day.

Would a trust be the best way to go about this? Custodial investment account on something like Fidelity? Just doing my basic research right now.