Language is a tie to family and to culture. If parents do not pass on their language to their children, the children will not have the benefit of growing up with significant ties to the parents' culture. While, when they are young, this may not be such a big deal, when they are older, they will realize how disconnected they are from their parents' culture.
Of course, knowing more than one language will be an advantage in life. If parents have the ability to teach their children more than one language, they should do so. The children may have more academic and employment opportunities in their future if they have a command of multiple languages.
Yes, i believe children should have access to both languages, they will learn both easily being young and also it would become for the child and option to get better jobs and learn more things while growing up. It easier for a child to learn at home the language hearing it all times than rather being at a school at an older age.
I believe that the language that should be taught to the fullest is the language that is primarily spoken in the country that the family lives in. Not everyone can learn multiple languages, including children, and if a child is having difficulty learning both then the focus should be on the one spoken in the country/ location where the child resides.
I think that, if a child can handle the learning of more than one language when growing up, that they should be able to and encouraged to. Otherwise, it's not always the best idea.