I personally had no issues being raised through the medium of English at home and then being exposed to another language (Welsh) via my childminder and playgroup. In fact I was a ridiculously chatty child with no delays of any kind.
My brothers took a little longer to speak under exactly the same circumstances, and my sister was very quick to speak in both languages!
It is well documented that some bilingual children take a little longer to speak in both languages, but apparently this is not due to confusion. They know who to speak to in which language but just have a lot more information to assimilate. The aim is consistency. I know a five year old who speaks five languages! One each from parents at home, another two in school, and the fifth through his nanny and her friends!
Children are remarkably capable, and the benefits of bilingualism extend far beyond the realms of just language.
Good luck, I'm sure you'll make the best decision for your family