Get your Dad to help you - he will being a regular cyclist, and be quite 'chuffed' on the quiet. My daughter has been in the 'I'll mess my hair/make up' for a few years - won't listen to dad and older brother telling her to use the granny gear up a trail.... nope, it's not a little lump you can honk it over, you will have to pedal.
Engage with Dad, he will help you -he won't have liked to push. You've got to get 'cycling' and you can't push it. You will be your Dad's best mate...
I work with many young/healthy/fit/pretty/handsome folk in my office - all mid to late 20's, no exercise, all busy with life/social... they look in horror at a few of us that are married, with kids and we turn up with broken bones at work because we are still active in the sports we enjoyed as a kid... we are all far fitter than the kid... so you Dad wasn't wrong....
Talk to Dad....