Tax on interest/income from investment account

Saffagal

My mom died very unexpectedly and left me far more than I realised she had, so I was not expecting to receive this amount of money at all. I don't  believe I have a short/medium term need for it and would like to look after it not fritter it away.
My mortgage is fixed for another 2 years at 1.39% and I am already saving/have a pot to do a large repayment once this fix ends, I'm earning more in interest than the benefit of overpaying right now. 
My work income covers my living expenses, I live within my means, and I very recently upgraded my car from savings. 
I am already paying into a pension (NHS) and have been consistently for a number of years. I also have a small second pension fund. 
I have allocated 18k to invest in a jnr ISA for each of my children out my inheritance (this is excluded from the 100k) and both children have a savings account already.