I'm not going to give you financial advice as I think everyone covered it above....
I'm the same age as you with kids a bit older. I wanted to comment on the burnout piece if I may.
You have achieved a lot and are very secure and have weathered the storm in getting there - well done.
Similar to you I had a pretty high pressure (but not as well paid) job in the past and was on the same trajectory. Stress, juggling and a lot of late nights, early starts were par for the course for me. I did a Post Grad, then a Masters while my kids were very young and the sky seemed the limit.
Like you I felt really burned out, no time to enjoy success, constant knawing feeling of not being on top of things. Mentally not great.
I ignored the burn out feelings for a long time, started to work with a therapist who told me in no uncertain terms that I needed to radically change. I didn't really listen.
I was flying to the states a good bit for work and feeling more burnt out than normal. In 2010, pre conference, just off a plane, in a hotel in the USA I suffered a burnout that left me hospitalised and in a psyc secure ward. The worst time of my life. I came home, got referred to a psychiatrist, emergency team and my GP. I spent nearly two years in a state of constant panic, anxiety and at times very low mood. I could not work, I didnt hear from my colleagues, work dried up. I started working with a psychotherapist to see how to fix this and I developed a great relationship with her. She passed away suddenly. Rock bottom.
I was really lucky - I found a phenomonal psychotherapist who pieced my life back together. He got me living, got me to see life differently . Got me to listen to the voice inside that would not accept my efforts.
I went freelance, I developed a chronic pain condition that Iive with today. I worked as best as I could, I spent so much time with my family, I upskilled, managed on very little money and got better. Its now 13 years from that time. I'm happy, relatively well, have enough but not lots of money, I check in with my psychotherapist, I am a help line volunterer for the Samaratains, I am re- training to be a psychotherapist. I play cards with my kids every day and watch them grow up before me. Simple stuff.
Why am I telling you all this stuff? Because we only get about 4000 weeks on this earth. We get a daily small oppprtunities to interact with our kids and then they are gone, they disapear and they grow up and away.
I think its great you got financial success but be careful about looking for more. Why more? You are 50, same age as me. Time to reflect, maybe think about what you want, not ignore the burnout feelings. I ignored it and it taught me a big life lesson. Now I'm the happiest I have ever been, I do not have the financial security I wanted but I don't have stress or a boss or a feeling I'm not achieving. I'm doing OK. Maybe the big push for security is your thing but don't let it de-rail your life, look after yourself, we are fragile sometimes, we lose our way, get sick, things happen quickly. If you are feeling burnt out now have a plan to not get burnt out and put it into place.
Hope this is not too much of a big long saga but nobody told me what burnout could do.
If you are looking for the bigger house/ car/ whatever bear in mind you are creating more constraints and difficulty for yourself - sometimes for something you don't need. I wish you the very best, happiness, health and contentment. Your kids are young still but gone soon enough. Create experiences!