If you see a person who has second language acquisition, perhaps you will think that he is so great. It seems comprehending other languages become necessity that a lot of people should have. Actually, it depends on the way your kids needs those other languages or not. Some colleges do not require second language acquisition as the entrance requirements for their new students. But some others do need second language as the important requirement. Therefore you have to set the kind of curriculum which you will apply to your kids. You need to decide about the importance of teaching another language.
This is also due to the fact that not every parent knows a second language. It means you have to hire another teacher to teach your kids and you have to supply the language teaching equipments at home. Although it is considered more expensive, you have to know the benefits. Learning a new language means your kids learn about other people culture. Language is not just a matter of verb tenses and grammar, but more than them, it is the way for your kids to know more about the world. They will learn the differences between languages in positive ways.
Moreover, your kids will develop their critical thinking from the differences. Suggest and support your kids to practice in a small amount but regularly. At the beginning perhaps your kids tell you they do not want to study that language. In this case, you should explain the benefits they will get in the future although today they have to work hard. Tell them that the language they speak now is not spoken in all countries in the world. Another fact says about the biggest complaints about Americans is that they think everyone does speak English. So, a lot of American will insist to speak English in a non-English speaking country.
So actually, learning other languages will give any disadvantage to the learners whether they are kids or adults. There are higher opportunities for them one day to visit or correspond with people in other countries such as being a guest, tourist or a missionary. What you need to do now is arranging the right schedule for the kids to study other languages as the part of their homeschooling system.