Good evening from Japan,

I usually teach Business English/ESP and have absolutely no experience teaching kids.

A Japanese friend of mines have 3 kids (18 months, 3yo, 5yo) and wants me to teach them some English.

I'll probaby use OUP's First Friends or Tiny Talk with the older kids. But the 18 months toddler... frankly, I have no clue.

Any suggestion(s)? Any textbook/activity book you recommend?
First Friends or Tiny Talk are both made for kids ages 3-6. I really don't know what to do with the little one.