I'm skeptical of a couple of things here.
> They will be in 6th grade next sept.
> My boys know php+ python, Go, rust, obj-c and learning solidity.
That's so impressive for a 5th grader that I'm questioning whether it's true. It takes years to know all of these languages. And if it were true, they likely aren't focusing their time well, both with regards to coding and other school material. Learning more than a couple of languages doesn't do much at that age.
Also, if they are ahead of their peers, why not give them more 7-8 grade material? The idea that they should be learning smart contracts and stock trading before they learn high school algebra is absurd. There are much more appropriate electives that you can pick at that level.
If your kids really are talented and ahead, let them get further ahead and give them opportunities to learn. And by learn I don't mean redundant programming languages and cryptocurrencies. Otherwise you're modelling your kids after a middle-aged developer who wants to buff up his CV so he can get a coding interview.