Excuse me, I forgot about this post.
It’s a little difficult to recommend a series of books for all ages, as they will almost certainly be ‘wrong’ for most of those age groups. Kids’ cognitive and social abilities are very different, as they develop and books are generally written to appeal to a 3-4 year age spread at most. Few kids series’ go far beyond an intermediate level, also.
Caves in Taipei have a ‘British English’ section. OUP, CUP and Longman are generally of good quality.
Don’t forget, though, a book isn’t a curriculum and nothing covers everything. It may be a good idea to approach it from the angle of ‘what am I trying to achieve?’, rather than which is the book for me.
You probably need to supplement a general course book with graded readers; look at OUP and Penguin stuff.
Stuff I Like
Happy House/Happy Street/Happy Earth (OUP)
Dolphin/Bookworms Readers (OUP)
Backpack (longman) looks promising but never used it.
English In Mind (CUP)
New Opportunities (Longman)
Energy (Longman) not bad.
Cutting Edge (Longman) For beginner to Int
Headway (OUP) Upper Int/Advanced
English File (OUP) is not bad
hope that helps/is not too late.