Hi OP :)
I am a barrister, albeit one who went into it at as a first career.
This statement of yours really stood out to me:
it's so tough, I desperately want a career I can be proud of, but it's very difficult with young children, I just wish I'd been more career focused at a younger age and already had this all sorted
This to me is the crux - do you think that perhaps it is not a career in law that you want, but the things that a career in law represents? Achievement, status, money?
I am not criticising you wanting those things - many of us do. But there are other ways of achieving them. You should only go into law if you are 100% committed to every aspect of it - and that includes a good understanding of the many downsides.
Through mini-pupillages (barrister work experience) and scholarship interviews, I see many many women who are studying for the Bar as a mature student. Women who have spent years raising children and have now decided that it is now their time to shine.
In many cases they have spent many thousands of pounds (it now costs around £40,000 to do a degree and train as a barrister without scholarships or extra funding). The truth is that the Bar is romantic - the Inns of Court are beautiful, the job feels exciting, and I would not do anything different.
But there are many many downsides - self-employment sucks, it is ridiculously competitive, I regularly have to cancel engagements because I get a last minute case in for the next day I need to prepare.
I am just not sure that every entrant to the Bar really has a full understanding of these downsides - they spend the money and then find out the realities later on. I feel particularly sad about it when I see a mature student wtih children. These are intelligent women - why are they putting themselves through this?
I have thought long and hard about why that might be, and I think it is partly to do with the reasons you identify - people who perhaps did not fulfill their potential when young and now have something to prove to themselves. Law is a good marker of having "achieved".
But the fact is, that is not a good reason for going into law. My advice to you is to do some work experience and see if you actually like being a solicitor. A high street solicitor out of London has a very different life to an associate at a Magic Circle firm.
I would then suggest the CILEX route that has already been mentioned. Both the SRA and the BSB (the regulatory bodies) are very focused at the moment on creating diverse pathways into the profession. A CILEX qualification in a few years will probably enable you to do anything a solicitor can do. (Whether that is right or not is another question).
So, to sum up a ridiculously long post - I would have a re-think on your motivations. You can (and I am sure will) succeed and realise some of those earlier ambitions - but please do not do it at the expense of yours or your family's happiness.