In Helsinki, if the weather is suitable, I'd take my 75 year old mother-in-law to a sightseeing by boat. Then she would love the rhododrendron park in North Haaga, if timing is right for blooming. Taxi would be easiest, ok with bus too, maybe 20 mins from Port in normal traffic.

But she is and has been living in the countryside nor traveling much so everything would go :D

Could think something else for you, if you know some prefereces.

Regards, Kati, in Kangasala, Finland