Its only a suggestion but the 5 hour Zadar to Pula ride is not a big thrill. Its in a catamaran meaning you do not sit out on deck, and then as you say finding the car, paperwork, etc..will have youi out of Pula at 9 pm and probably close to 10 pm at your destination. Why not simply pick up the car in Pula, drive up the coastal road to Rijeka, its scenic, yes about 4 hours but at least you can stop and do at your own pace and your final destination is an hour down from Rijeka!! Its less time, less stress, and much more enjoyable than your long boat trip, and again nice to see fellow Canadians coming to the area, stop by here in Opatija for a coffee its right on he road between Rijeka and Baie!! If its La Grisa as DannyG mentions, super place!!