Concur with @Ben about HTML5 (see disclaimer, below).
Recommend investigating the Computer Science Field Guide (don't be distracted by the TLD, the Curriculum Guides include AP-CSP. (and New Zealand is more advanced in this field than many?most other countries!) The activities are a mix of 'play' and serious (thinking) challenge.
Just as HTML's declarative approach is not an ideal preparation for procedural languages, many are also concerned that 'going straight to the computer' is an invitation to 'consumer-mode' thinking - for what do most prefer to use their tablets/portables? Whereas "computational thinking" is the desired outcome. Accordingly, please review the CS Unplugged series, which invites the discovery of many CS concepts 'in real life', before implementing solutions in Scratch or Python. (I regularly take-on adults who say "I couldn't do computing" or "I'm hopeless at all that math-stuff" with CS Unplugged's exercise in finding the highest number from a list, using values 'hidden' inside take-out cups - and before you/they know it, describing their thought-pattern reveals an algorithm!). Thus, design-first, develop tests/a proof, and then implement on-computer! NB much of that material seems aimed at younger students, but will depend upon their previous experience.
For yourself, and in the same pattern, please review Teaching Computational Thinking. NB the course as-described seems longer/more-involved than it needs to be, depending upon your own background and judicious choice of topics to suit your target age-group.
Regards =dn (Disclaimer: I use the edX platform for HTML5 training (adult/vocational))