If you mean on the ferry, I am not sure of the rules. You may want to take the ferry to Port Aux Basques inseatd fo Argentia. Its about half as long (16hrs compared to 8Hrs)
The RV parks here do have leash rules.
Are you planning on renting when you are here? If so, some places have a no pet rule for their rentals.
There are many scenic drives here. Pick up a Newfoundland & Labrador traveller's map. They can be picked up either from the Newfoundland Tourism office. It will show where these drives are. Some are longer than others. Just remember that our island is bigger than it looks on most maps. Google Scenic Newfoundland Drives, it should come up.
If you have any questions just PM me. I will be doing some travelling with my parents in July and in the process of scheduling their trip. If I can help, I will.
Yoou asked about phones. There are no special phone requirements here. Some providers here have spotty signal (Rogers), but Telus and Bell have no issues.
Most parks here have mostly seasonal lots so be prepared to have full parks. Rates here are comaprable to most other places in Canada.
If you are here late June early July you will be here for iceberg season. Check out Twilingate or St. Anthony. They are a long ways apart so plan accordingly.
Check out the town websites where you plan to visit. There are lots of festivals all over the island. Just google the town name.
Dan