I have used the 5.5 Clicker game as a summative assessment along with the test provided. When you ask about making something a Practice PT, I assume you mean writing to a rubric modeled after the official CB Create task rubric. I agree with @lanna.mack that making 5.3 a full Practice PT would make addressing the official rubric very difficult. However, you could choose to use it as an opportunity to practice writing -- focusing on Question 2B.
With the limited amount of time, you will have to decide how students get access the advanced concepts in lessons 5.5 and beyond. Variables, conditionals and looping will be critical in developing complex algorithms to meet the Create task's requirements. You may be able to leverage some of the work completed in Unit 3 to adjust the pacing for Unit 5. You may look directly teaching some material and reducing the amount of activity 'bubbles' you require. You may want to look at 5.10 Color Sleuth and 5.14 Image Scroller as case studies.
In the end, it is really important to let students know that their work on Code.org is just the foundation for their Create task. If they decide to do a Clicker game, they will need to add significant original work to meet the requirements of the rubric.
Here are a couple of threads from last year that may help.