bilingualism help!!!

So right now we are living with my SOs family while searching for a home to purchase. My SO speaks English but knows Spanish and his parents speak only Spanish. His sisters sometimes speak to my daughter in Spanish and sometimes in English. I'm worried that since there isn't a real routine going on and the exposure to the two languages is random it may lead to a speech delay. My SOLs son is four and was taught language the same way they are trying with my daughter and he still has not began to speak. This is where my concerns are coming from. Anyone have any advise on this??