I would add the addition at flame out next time.
Also, don't use the LHBS stuff in the package, source bitter oranges yourself, or use navel orange zest in a larger quantity if the bitter orange is unavailable.
My gripe with the dehydrated bitter orange that is sold at the LHBS is that it has pith along with it (it is very bitter). You really only want/need the zest.
I have brewed a Witbier at least every year since I have been brewing, and I am refining my recipe. I am actually drinking a pint of my latest Wit right now! I brewed 10 gallons on 3/14, ran through 1 keg and kicked it last Friday, tapped the second 5 gallons Sunday...delicious!
FWIW, IMHO, Witbier benefits greatly from true Seville orange zest, I use about 6 oz (wet) at flame out for a 10 gallon batch. Indian corriander is an absolute must, you cannot get the same aroma/flavor from store bought (citrusy vs celery respectively), and a small addition of lavender or chamomile is a unnecessary yet nice addition. To conclude, and once again IMHO, White Labs WLP 400 is the superior yeast for a Belgian Wit, I have not used anything that even closely compares.
In your situation, RDWHAHB, toss the bitter peel in (as long as it is the dehydrated type--fresh peel will undoubtedly have a good deal of wild yeast on it), and follow the instructions.
Do further reading, brew more, you will find that infections are much more uncommon (if you follow sanitary practices) rather than contamintion which can be somewhat easy without careful attention to details.
Good luck I hope your brew turns out magnificent!