Best $ to/from PEI are ferry to and bridge from. You pay when you leave. Bridge costs less.
Check fuel prices all 3 Maritime provinces. All are regulated. If it's a week when PEI is less, it will pay you to tank up. Likewise in NB or NS.
I'm not going to guess reservations. Figures on visitors from US are high because of exchange rate and maybe our dry summer. Forest fires in NS appear to be solved.
:B