So, £100,000.
£6K pay off debt.
£10K car? (Family car bought outright second-hand, 3ish years old?)
£5-7K windows? Depends on how big your house is.
£2-3K carpet?
So, you've got about £75K now.
You need 3-6 months regular outgoings in an easily accessible account. Say £15K? Lots of people recommend Premium Bonds.
What are your pensions like? You need to save into your pension before you save for the DC. By all means put some away earmarked 'for the DC' in a couple of S&S ISAs, or similar, that you can leave for the longer term, but keep it in your names - then if you need it you can access it. So maybe £5K x 2 'for the DC'.
Now you've got £50,000, if you haven't paid anything into a pension yet.
In this scenario, I would not spend £40K of it on a house I was not intending to live in past 7-8 years, unless I was sure it would add value.
So if you spend £20K on doing it up (bathrooms, kitchen, decoration?) then you have £30K left. Which I'd pay off the mortgage, if pensions were sorted. If not, I'd whack it into pensions but keep a bit for a lovely holiday.