Adding Flavoring before bottling...how will this effect priming?

So I'm doing this O'Fallon's Cherry Chocolate clone...

It calls for alcohol base chocolate extract and cherry flavoring. I am making my own chocolate extract with vodka & cocoa powder. And my plan for the cherry is to use juice from marchino cherries that I have handy...

The cherry juice is a pretty thick syrup that I'm certain contains a good deal of sugar! If I use this juice right before bottling, should I cut back on the priming sugar/ omit priming sugar entirely? I don't want to end up with explosive bottles or over carbonated beer.

I had planned on racking to a secondary to cold condition the main batch. I could try bottling a few 12oz bottles early and see how using only the marchino juice as a priming sugar works...and a couple bottles with marchino juice and the standard amount of priming sugar per bottle. For comparison sake.

Any thoughts?

Ok, so upon reading the label on the cherries, I think I may have answered my own question....

There appear to be enough preservatives in them to inhibit any carbonation.

Any suggestions on what will give a nice round cherry flavor, and not impart cough syrup flavor?