Lump sum for mortgage?

What is the best use of $100k? My grandmother passed away and I ended up with a lump sum.

54f employed (175 k/yr) and single.
Rrsp maxed
Tfsa maxed
About $200 k in non registered investments

Db pension that will pay about $50k per year at 60.

Mortgage current $300k @4% (house value about $700k). No other debt.

Current plan is to retire in 2 years.

So, the $100k. Do I put it towards my mortgage, or invest in non registered accounts? My kids are young adults, RESP for tuition, etc. Both have max in their tfsa.

Many years ago someone told me to never worry about the mortgage. And so for many years I didn’t. When married we travelled a lot, spent a lot of money and had good lives. Of course, then we got divorced, and I bought out the house so I have more mortgage than I would have planned for 54.

Is paying it down the right next move?