Can someone explain - not financially savvy!

[Bimbomboosh]

Wondering if someone can help explain something for me:

I have just opened a savings account for my baby at 2.5% interest for a year and would like to save the maximum of £100 per month.

Husband thinks I should pay £100 a month off our mortgage instead. Our interest rate is 1.89% until end of 2023 and we have £135000 left.

I can't afford to do both as I'm only part time at the moment.

Which option will save more money in the end and why? I feel a bit stupid for not understanding or being able to work it out easily.

Just to throw a curve ball in I've saved into pensions for my kids (currently pay £50 a month each but started at £20 when my eldest was born - who is now 12).
I did this because I read that if you save a monthly amount from birth to 18years it works out more than saving the same amount from 18 years to 65 because of compound interest (I have no idea if this is true!).

I would save for your child in a form that you can access e.g. an account the parents can withdraw from as although the long term goal is uni/house deposit you might find they want/need a certain thing when money is tight e.g. a computer or to go on the school skiing trip at £££.

Personally (and I know a lot of people disagree) I don't fret about the mortgage - just leave it ticking over its 30 years. I figure I should have less obligations paying it in later life than I have now trying to provide a good standard of living for the kids. My partner and I limiting our work due to childcare. I might feel different if I needed to build equity to move house though.