I agree about speaking to an IFA. With the oldest in tow. There are probably things to consider that I wouldn't trust myself to be able to spot. That is an amount of money that is potentially life changing, if handled well, and potentially nothing more than a nice holiday, or a car, if not.
But, broadly speaking, I would still be aiming to take max student loans if at all possible. And personally I would be investing. It is a balance, as Redcart says, of when you want the money. This will determine your "wrapper" ie pension/LISA/JISA/ISA. For the late teen it would be a combo of LISA and ISA, with a view to house deposit, dripfeeding the LISA to the max each year to get the max government top up. And possibly using some to start a pension. For the littlies it would be filling up JISAs for a few years, and a bit in a pension.
What to invest in within these wrappers? As Redcart says, that depends on your level of knowledge and confidence. But essentially you want to be mainly in equities, and personally I would go for a well diversified mainstream fund/etf.
With the wildcard investments, ie bitcoin or individual shares. I personally wouldn't. But if your oldest wants to play, allocate a small proportion (maybe 2 to 5 k) to do this with, and stick to slow and steady for the rest of the money. And depending on the actual amount, you could consider a similar amount for oldest to allocate to experiences (when covid allows) like travelling etc.
It depends a bit on your (as parents/family unit) financial situation. It helps you as you won't need to think now about helping them with house deposits or pensions. So might ease your own savings plans. But it is impossible to know without knowing what your position is.