We just sailed from Vancouver and used the Skytrain both ways to the Pan Pacific. Riding on the weekend, the total cost for 2 adults and one child over 12 one way was around 8$CAN. Children 12 and under can ride for free (up to 4 with one adult paying a full fare) and are expected to pass the gate with the adult. The ride from the airport takes around 25 minutes to the Waterfront station. There were plenty of seats and space to put our luggage, but that might differ if you are traveling on a weekday during rush hour.
There are elevators at both ends of the journey, but also escalators if you can handle your luggage on them. The walk from Waterfront is easy and safe and is around 5-10 minutes to/from the pier. Since there are cruises sailing pretty much every day, there are plenty of tourists in the area walking around with luggage. The only situation where a taxi would be better, unless you have mobility issues, is if it’s pouring when you get to Waterfront or on disembarkation morning. At YVR, the access to the trains is well#marked and covered. On disembarking, you just need to folllow the ‘Public transportation’ signs and walk to the Cordova entrance of the Waterfront station. The first Skytrain station you encounter after coming out of the cruise terminal does not lead to the Canada line trains.