I would assume that AB+BC in one year would be a struggle. Currently, in my school PreCalc and Calc AB can be taken together in one class and advance the student to BC. I was too lazy to take the class last year during my sophomore year because I was scared that it was too hard but looking back, I learned almost nothing in Precalc-It was basically a review of Algebra 2.
If your kid has been doing fine in math, then the advanced course would be the better choice. AP Calc AB is not too hard and all the curriculum comes together and builds up on one another.
Imo, it may look better if your kid goes from PreCalc to Calc BC because it will show that your kid skipped Calc AB