I would have to agree with other posters, I don't think becoming a solicitor is the ideal career path at all for happy work-life balance.
I worked in private practice in the City (corporate) then went in-house for an IT company, with offices in and out of London, hoping the latter would give me more of the work life balance and less stress, but you just exchange one type of client for another. I worked "part time" after having children and tried various roles but was just as much at the client's beck and call, whether that client was a an external corporate, in-house business division, senior management or the procurement team. Conference calls and client meetings and negotiation meetings are not set or determined by you. I stopped work while my children were all still primary school age, even with a really understanding and flexible nanny and supportive husband it became too much for me. It would be less difficult with mine now they are secondary school age but in a funny way I find they need me more in a different way now. Just my own personal view.
I don't think age is a factor, and you have a huge amount to offer, particularly in house with your sales and business experience. There are many strands to law, but company/banking/finance/ commercial/litigation/property would be very demanding. Private client work such as trusts, tax, wills, probate and administration are less deal-time driven so may offer more flexibility. Other women in my group of solicitor and barrister contemporaries chose to go down the professional support, company secretarial, or training and education routes to work around having children, but as another poster has said, that was leaving the hard-core legal bit after gaining experience. Law firms do need marketing, PR, business skills people and the big ones take on people in these roles specifically more and more.
Could you use your current skills in an industry, goods or service, that is more specifically family/working mother focussed, and hopefully offer some more flexibility. Whatever you decide good luck and I hope you find the answer - please do share it if you find it!