How long do you plan to be on your career break? If it is more than 2 years and you plan to get back into something equivalent to a trader, you should do something that will keep your hand in and your industry knowledge relevant.
Hence being a consultant along the lines of what @Ponderingwindow suggested is a very good idea. You will get the highest remuneration from your time if it will be flexible when the work is done and ideal if it can be done remotely. However, I don't understand enough about what a trader in a bank does but it does not seem like being a trader would easily lend itself to such a consultancy.
If you have worked in the corporate world in a bank, I agree with @ItsAWonderfulLifeforMe that bar work or deliveroo deliveries isn't likely to cut it for you. If you cannot be a consultant, then perhaps online tutor for maths might give you the flexibility you need for your skillset. But it is not likely to advance your comeback career unless that is teaching.
An alternative is to do a part time course in your future career. You mentioned financial risk management. But doing a course would not bring in money during this time.
Are you seeking flexible work for the money or to keep your mind active?
Personally, if you are the main earner before, it makes more sense for you to go back to finding a ft job and use childcare or have your dh be the SAHP.