As a couple you need to work out your priorities. He's been brought up to be frugal, you've been given handouts by your parents for years and maybe don't worry about having savings. Yes?
The fact you don't have £10K 'spare' to splurge on a big holiday says a lot about your finances.
If you both have good jobs and good pensions (are they public sector?) you sound as if you're maybe not being very money-savvy, bearing in mind how much help you have had from YOUR parents (house deposits, gifts, etc etc.)
We have 15 years left on our mortgage.
I don’t think he’ll put it towards that. In fairness we don’t have much in the way of savings (though no debts either) so it would make sense to invest it.
If you have few savings in your late 40s/ early 50s, yet you both have a good income, something isn't right.
Where is your joint income going/gone?
IMO you should focus on paying off your mortgage.
Investments go up and down.
Not being unkind, but £80K is not a lot in terms of investment and growth.
It certainly won't make much difference to a pension pot.
I think regardless of what you decide on the holiday, you need to find a good indie financial advisor. Ours is worth his weight in gold- literally.
I'd not consider a pricy family holiday as a priority. Your children can travel once they leave school/home. Mine backpacked round India, interrailed across Europe, and more, under their own steam and on money earned while at uni.
Put your own long term finances first.