Lots of people ask me "Why should I teach my child a foreign language?" I first respond with "Why not?" Then I go more into detail with my answer and explain how helpful it is to learn a foreign language at a young age. It's a proven fact that children learn languages best if they start learning the language before the age of around 7. (The exact age varies depending on which articles and research you read, but generally it's around 7 years old).
Also, studying a foreign language will help with their math skills now and when they are older. Language and math skills are highly linked, so studying 1 will help the other.
Another reason and perhaps my favorite is that through studying a language it opens the door to the world to your kids. When you teach them French or Spanish or any language you can teach some culture and geography too. This will really open their mind and help them to see the bigger picture of the world that they live in.
And if you are a homeschooling mom I think it's important to have some 'electives' in your curriculum, so why not a foreign language.
The next question I usually hear is "Which language should I teach?" You can teach a language you are familiar with or you can choose a language that interests you and learn it with your child at the same time. As long as you and your children are having fun, then it is all worth it.
As for me, even though I've studied Spanish, Japanese, French, Latin and a few other languages, I chose French to teach my children because I've always loved the sound of the French language and I've always loved French culture.