Loads of great tips, thank you very much for all your comments.
My daughter's hair is beautiful and I tell her that every time I comb it. I always wax lyrical about how, when I was little, I often wished I'd had hair just like hers (mine was a nearly completely unmanageable, comb-defying afro with a mind of its own
). I point out the many positives of having hair like hers when styling it, explaining how much character her hair has, how versatile It is, how well her styles last (for 3 - 4 days for some braided styles) and how amazing she is at maintaining her hair styles by herself.
However, despite all these genuine positives, it does have its definite challenges...
It was my own local specialist hairdresser of African & Caribbean hair who suggested the two treatment options I listed in my OP. These treatments are both new to me (hence this thread), but are apparently commonly used on dual-heritage hair. Treatments and products for my own kind of hair are too harsh or just unsuited to my daughter's. My hairdresser tells me that both treatments are used by children as young as 7+ years as they contain only natural ingredients which are designed to strengthen and nourish the hair. They're supposedly not like the straight perm (or relaxer) system, which I've used in the past, that break down the hair folicles to eradicate the 'kink', but which then end up breaking the hair in the long run (happened to mine).
I already have tried a number of different spray-in and leave-in conditioners and hairdressings and am running out of patience with buying products which promise miracles that, although they may work well for other people, just don't work for my daughter. Or leave her hair with an unseemly residue or sticky product build up. Just as afro hair is as individual in texture, strength and character as its wearer, so is dual-heritage hair. So some YouTube tutorials haven't worked out too well for her hair in the past.
Currently, with use of weekly washing and moisturizing conditioner, followed up by use of spray-water and coconut oil for styling, we're managing ok with her hair at the mo. Having afro hair myself, and having grown up with dual-heritage cousins, I am comfortable with styling my daughter's hair with creative, pretty plaits which earn her compliments from many lovely parents (and some odd, judgemental, and sadly, sometimes some quite frankly, rather openly hostile, disgusted looks from others - but that's a whole other thread 
- we live in a predominantly white area). But, as the afro content of her hair is so prevalent, it is tough for her to endure the styling process in this way. We have easy access to the Wolverhampton and Birmingham areas.
Hopefully I have answered all questions. I won't be able to provide a photo of her hair, sorry, because it is currently styled in braids so you won't be able to see the texture. However, I will certainly look into the many suggestions made above. Thank you all so much 

and please, please keep the ideas and comments coming!