Most textbooks won't have a lot of kanji, not in the first volume or so...
This is because they're not aimed at people who uses RTK! But if you've already done some Vocab, and/or if you have some time to spend on Tangorin (
http://tangorin.com) you can add some kanji to these sentences by yourself.
Just try not to overdo it!
Some words are ususally written in kana even if there are kanji for them. Words expressing time (the day before yesterday, yesterday, today, tomorrow, the day after tomorrow... the year before the last, last year, this year.....) are usually written in kanji (or numbers + kanji: ３時 instead of 三時). The main exception is for greetings like "konbanwa", "konnichiwa", which usually are in hiragana.
I took a look at the vocab of the first two chapters of Genki, this is what I think:
All "Majors", "Occupations", "Family", "Places" can be safely written in Kanji.
"Words that point": None can be written in Kanji
"Food": All can be written in kanji (but oishii is most common in hiragana)
"Things" Everything that is not in katakana could be written in kanji
(maybe except boushi?)
Since you're starting from chapter one, which vocabulary also involve countries, know that a lot of countries in Japanese have both a name in katakana and a name (with a different pronunciation) in kanji. For now and for a long while, stick with the katakana one, which is really more common. You'll pick up the kanji ones in the future if needed.
This applies to western countries. Asian one will only have the name in Kanji, so go for that.
