Shannon falls (near Squamish) is a very short flat walk from the parking lot, Bridal Veil (near Hope) falls are very accessible too.
How about Harrison Lake beach & a visit to Minter gardens for a day trip? Hope slide is a bit further up the road on hwy #3 but worth a 20 minute look about.
Pitt Lake is always worth a visit, a nice easy dyke walk-you could even rent a canoe & paddle Widgeon Slough, its very placid & easy even for an older fella (& different!).
The ferry ride to Bowen Island always goes over well with my visitors & Crippen park is right there & very easy to stroll in.
Queen Elizabeth park & conservatory are good too, & they may be closing the conservatory soon. Van Duesen gardens are great too.
Don't forget Grouse mtn tram & lots of easy stuff to look at the top. Guests always like looking over the Capilano dam en route.
Hope these help.