Hooji-cha

I did an internet search on hooji-cha and it says it is roasted green tea. Is it recommended for children (the store clerk suggested hooji-cha for children), but if it has caffeine, is it really recommended?

Caffeine in Hoji-cha contains 30 mg in 150 ml. Green tea also contains 30 mg. I don't think it will be problem if children drink it in common sense quantity.

Mugi-cha(roasted barley tea) contains 0 mg caffeine which is very popular dink for children and pregnant.
http://xn--nyqy26a13k.jp/wp-content/uploads/2015/07/xucaizvNRM2TEtK_EB...

My recommendation is bancha.

http://www.myjapanesegreentea.com/kyobancha

Bancha contain no caffeine, so it is popular in Kyoto Shiga areas.

Especially it is available as akachan banch which means baby bancha.

sen-cha, ban-cha, and houji-cha contains caffeine in similar levels.
http://www.kyo-chikiriya.com/blog/tea_about/%E3%81%8A%E8%8C%B6%E3%81%A...

ban-cha is a name of lower class of green tea leaf. thus, it is popular.
mugi-cha is generally a summer specific tea. this is not produced from tea tree leaf.

water, cooled down after boiling tap water,湯冷まし, is fine for a baby, I think.

I am sorry my explanation in not correct.

Ken's explanation is correct.

http://www.thefragrantleaf.com/caffeine-and-tea

The top bud or leaves contains much amount of caffeine,
but lower part of the tea bush contain smaller amount of it.

The leaves of baby bancha are very big size, so they contain caffeine but smaller amount.