BUT beware.  Your children will be exposed to idiots who have no issues talking of such topics like sex other things you might not want your child to be exposed to.  I am not trying to scare you, but please if you care enough to home school certainly you don't want your children tainted by kids with no discipline in the internet.  I recently have found a site that offers live lessons in Japanese 1 on 1 so that your child can have a live teacher.  This site currently charges around 20 dollars per 50 minute lesson.  I have not tried their services but they look like a reputable outfit.

ALSO once if your child is familiar with Instant Messenger programs they can usually find a Japanese child close in age that wants to learn English.  Instant Messenger programs all the TALK ability and if you find a Japanese friend then one day they can talk only English and other days they can talk only in Japanese.  This is a GREAT way for your child to be even more involved with Japan.

Learning the writing is a MUST!
I am always shocked to see people trying to learn Japanese without learning the writing.  There are three systems of writing in Japan.  ALL three are important.  The first 2 learned by Japanese children are called Hiragana and Katakana.  Both of these systems together are collectively called "Kana".  These are VERY easy to learn.  The Kana are phonetic symbols and do not have meaning by themselves much like the English alphabet does not have meaning when not part of a word.

Hiragana and Katakana each consist of 46 basic characters and then around 50 more characters that are made using the first 46 in combination.  IT IS MUCH easier than it might sound.  Hiragana and Katakana take only a few strokes to write and are nothing like the more complicated Kanji.

Even beginning students using our lessons on YesJapan.com are easily able to read Hiragana after the first 9 lessons since we integrate the learning into the lessons.  Some books and courses require the students to learn the Hiragana and Katakana even before the first grammar is discussed.  THIS IS A MISTAKE because it normally will overwhelm the student and might turn them off to the language.  Other materials will teach Japanese using the English alphabet.  This is referred to as Romaji in Japanese.  Teaching Japanese in Romaji is a very bad idea because the accent of the student will be strongly affected.

How Writing Improves Japanese Accent
When you grow up speaking and reading English natively English becomes part of you.  It is very hard to throw away what you have learned of the English language.  If you then try to learn Japanese using English spelling you will often read the word with an English accent based on your INSTINCT in English.

For example the letter combination "TO" in English is always read to sound like the number 2.  However if you learn Japanese you will have to overwrite that reading of TO and change it to sound like TOE.  This is a lot of strain on the brain.  It sends contradicting signals to the brain.  It makes learning Japanese harder AND weakens your accents tremendously.

If instead you learn the Japanese symbol for that sound your brain will learn THAT symbol represents that sound.  And since you have no preconceived ideas of the symbols you have learned you will naturally read it and speak it the correct way.  There is no conflict in the brain, and this makes the learning Japanese MUCH easier.

Over all my years of teaching I have yet to see an awesome Japanese speaker that didn't learn the writing!

Kanji writing improves overall Japanese fluency
Kanji, unlike the Kana described above, is much more detailed.  But I promise you Kanji will become your child's favorite writing system.  Most students come to like Kanji even more than the easier to write Hiragana and Katakana.

Why?

Because, Kanji is so cool.  Yes that is one of the reasons, but the most compelling reason to learn Kanji is the power that the Kanji holds in helping fluency.  When you have a grasp of even a few hundred Kanji you have a great database in your mind of the building blocks of the Japanese language.  Kanji helps comprehension SO much that I would be shocked if you didn't push your child to go the distance and learn the Kanji.

HOWEVER!!!  Do NOT start with Kanji!  Make sure your child can read and write the Kana first.  If they don't they will be dead in the water for reading Japanese, since Japanese requires Hiragana, Katakana and Kanji.   These 3 systems work in tandem to make up the Japanese writing system.  They are as important as UPPER, lower and cursive writing is in English.