I would use python instead of BASIC, if it was me. I also started with BASIC as a kid, but I remember each step up language wise (BASIC -> Pascal -> C) being a big satisfaction of "hey, it seems like this language is a lot better and I can do more with it." I would echo the recommendation to use actual code though. Language is pretty deeply hard-wired into human beings, and I suspect that the kids that will do well with breaking tasks down into scratch primitives would do equally well with python, and the kids who find python "too hard" or something would also not be able to do too much with scratch. Maybe I am wrong, but that's my guess.

My only other thought is to have some kind of graphical / game you can play / real world robotics angle to it. Maybe there's a little graphical ecosystem pre-provided, and they can write agents that can interact within the ecosystem and then see a visual representation of what everyone's agents are doing. I would definitely recommend to have a bunch of code that they can read, though; that was where my programming as a kid took a big step forward, was when I got a big disk filled with programs I could analyze and break down.