Type of Visitor visa

Hi,

I am wondering if a single entry visa to Canada will suffice for my requirements below:

1. On August 25th, I will be taking a flight to the US via Vancouver from London. I understand I need a transit visa for that even thoguh the stopover is only 3 hours

2. Later in August I will be doing a 7 night cruise (Celebrity Infinity) to Alaska from Seattle USA (arriving back in seattle USA). During this period there will be a couple of stops in Canada (again few hours each)

I feel a single entry would suffice since it allows for multiple entries to and from USA but I want to double confirm.

Appreciate any input.

Kind regards