Where should I put a windfall? Tell me what you think

I have an unexpected 'windfall' coming my way. I purchased $5,000 worth of bonds that were listed to last until 2074. Given the current low interest rates a lot of companies have been paying out these bonds and opening new ones with much lower interest rates. It's good business for them, but it means they're closing my investment and I'm about to have $5,000 in my pocket. I have some ideas what I want to do with it, but I'd love to hear your opinion.

Option 0: A neeeeeeeeeeeeeeeew car!

Hahaha, kidding. I had to throw this in here. There is no way the money is getting spent on anything but buying back my free time. 

Option 1: Put it towards the savings goal

This is the obvious option, I've got a goal to reach $20,000 in savings by the first of July (check my last update for February) but honestly that feels like cheating. The goal was to save $20,000, not to pull it out of my investments and put it into my savings account.

Option 2: Pay down some of the mortgage

This is an oldie but a goodie. Unexpected money can always be put towards mortgages, and the way mine are set up any excess payments can be withdrawn later free of charge. But it's not the best use of the money, the bonds were earning 5.05% and the mortgage is only costing me 3.99%. It'd be a net loss of 1% interest each year.

Option 3: Invest! But where?

This is where I'm headed! Invest! But where? The money is coming out of bonds with one of the Big 4 banks. Should I put it back into the same place, or somewhere different? The bank is offering reinvestment in their new bonds, but they pay about the same as my mortgage is charging.

I could drop the money into my Acorns account and dramatically decrease the percentage I'm paying in admin fees. My highest performing investment is in peer-to-peer lending (review to come!) but I have more than 20% of my non-real estate investment there already and I think that might be a bit risky, even if the 9.5%+ return is lovely.

I could also use it to balance my Vanguard portfolio, or I could dig in a bit more research and purchase some strong performing dividends shares, or another set of bonds.

If I get the time, I'd love to think about this more. But I'm also super aware of Warren Buffets advice that boils down to "If you don't know what you're doing, toss it in a low cost index fund like Vanguard and leave it there forever".

According to the stats on this blog close to 100 people drop by every day, most of you come from other personal finance blogs. I'd love to hear what you think (and verify that my stats aren't entirely robots!). The money hits my account on the 31st of March - what should I do with it?