Where to start upper primary (Years 5 & 6)?

Hi everyone,
I’m a primary computing specialist teacher, teaching K-6. I’ve been using the old Course 1 & 2 for my lower grades with great success, and will be switching them over to the new A-F courses in the next couple of weeks.
But now I need to get my year 5s and 6s started, and was wondering if I should start them straight on Course E or get them to do the Pre-Express course first? Most of them have never coded before, and some are reluctant learners so I want to make it really easy to start with so as to not scare them off! But at the same time, we have a limited timeframe. What would you recommend? Does course E assume any prior learning, as I noticed it gets into conditionals quite quickly?
Thanks in advance!