I think it is a pretty good seat for a granparent. It has a no re-thread harness which makes it easy to adjust the harness height when necessary. Also good if they transport other grandchildren in the same vehicle and don't want to swap out seats. It has seatbelt lock-offs which are helpful with non-latch vehicles.
I have two caveats. It is a relatively wide seat, so it will definitely consume alot of backseat space in the civic. Also, the harness adjuster is difficult to reach when rear-facing (what you pull to tighten). This may be a pain for an older person with any type of arthritis (not sure how old your parents are).
You need to be comfortable turning your DS at 35 pounds as this seat does not have a higher RF weight limit. My understanding is that it performs well forward facing, so I am ok with this for an older child.
Since I am not in canada, I can't recall all of what you have available to you. Is the safety first avenue available? It is a great seat and a little cheaper (here in the US) for a spare. The radian would work too and be narrower, but limits front seat passenger space because of the recline and can be a difficult install with just seatbelts.
I love my true fit and don't think you will be dissapointed. It should work in grandma and granpa's car for a long time.