I did Newfoundland and Labrador last summer (end of June through mid-July), but I was in my Honda Element. It was wonderful. (Labrador was quite an adventure and I saw some very brave souls on 2 wheels, but none on 3.) I would reiterate some of what has been said already. I hiked in sleet one day, and wore a t-shirt the next. Be ready for any weather from freezing to very warm, and for it to change in a heartbeat. And, although the main roads are pretty good, the secondary roads have potholes that are pretty intense. The same was true of roads in St. Johns.
We stayed mostly in St. John's at at friend's house till we headed toward the Labrador ferry. We didn't have a problem finding places to stay except around Gros Morne, using AirBnb and other online resources. We too stayed in Elliston and saw the puffin nesting area, but if you get a chance, take a whale watching trip out of Bay Bulls. We went with Gatherall's Puffin and Whale Watch, and it was amazing. The boat passes a seabird island with hundreds of thousands of seabirds, mostly puffins, and we saw a lot of humpback whales. Another naturalist site is Cape St. Mary's Ecological Reserve, where you can hike along the cliff to a gannet nesting colony (that was the freezing, sleety day, but worth it).
I took the overnight ferry from Sydney, NS, to Argentia, and, of course, we left toward Labrador. But if I were doing it on my Spyder (something I'm trying to talk my husband into doing), I'd take one ferry over (either the long Argentia one or the shorter one to Port aux Basques) and do a loop around the island. There was something of interest in every small town, and lighthouses everywhere. Oh, we also saw a lot of icebergs, even though it was late in the year for them.
BTW, I did enjoy St. John's! We used it as a base for day trips, and it's a very nice small city. There are good hiking trails above the battery, and the harbor itself was fascinating. Everyone we met was very friendly, both in town and on our travels.