4U Integration is so much fun!
The order of our topics was Complex Numbers, Curve Sketching, Conic Sections, Volumes, Integration - Partial Fractions, Polynomials, Integration (the rest of it.. haha), Mechanics, Harder 3U.
As you can see we did it all over the place, but we got through it! I would suggest maybe doing Mechanics straight after Integration and Volumes just so all the tricks of Integration are still in your head a lot clearer, but if you end up doing it in the order you've said there'll be no issue.