Lone Tree Hill is a beautiful hike [My fave! - Editor] but you won't be able to do it with a stroller unless you are prepared to carry it most of the way as it's pretty rough terrain and steep in areas.
Thetis Lake will give you a good work out and has a couple of trail options. You will need a stroller that can handle rough terrain for all trails. Be prepared to work up a sweat if heading up Seymour or Scafe hills.