Invest or be mortgage free?

[John Peter]

Feedback appreciated. I am almost 50. 3 kids all under 8 years old. I'm the sole income in the household. Retired from civil service with pension of 8k monthly. About 500k invested in a 457 from work. Just sold in NY and moved to FLA. Proceeds from NY leave me with 530k sitting in the bank. Here's where I need guidance.

I could pay off the new house and be mortgage free with almost 125k left to invest. My mortgage is in the mid 4% range and is about 1600 a month. I also just paid off my car. Now, I'm slowly finding out that living in or near a big city in FLA is almost as expensive as NY. 8k pension isn't going to stretch too far as time passes. So, at my age, with 3 school aged children, would you pay off the mortgage and invest the rest in a portfolio, real estate, or IRA (125k).. or leave +/-50k in the bank and invest the rest? (480k) Thanks for any advice. Btw.. I was a landlord in NY for 12 years before I had kids. I'd do it again, but I'm not 30 years old anymore.