Duvet Dilema

This weekend i bought Kit a single duvet, which is a little big for her junior bed now but she will soon be moving on to a single bed really soon BUT

1. She is Little Miss. Fussy pants. Don't get me started on why she doesn't like things, ie. because of the tiniest amount of green stitching shows or some other random made up excuse.
2. I am thinking maybe i'd like them to have matching duvets or ones that kind of match in some way as I will get Seb the same when he goes into her bed. Too cutesy or do you like matching?
They share the same room, here.
3. The freakin size thing. Why are duvet covers different sizes? Some are 140x200 and others like from Ikea and overseas are 150x200 or 150x210 or something else entirely which complicates it further. I mean do you just buy the styles that fit your duvet or buy two duvets so you can have any size? Seriously this is duvet trauma!

Help. Look. Options. I love the rainbows by Lulu and Nat but i showed her and all she said was "Does it have pink in it?" I said, "hmm, I don't think so." She looked away in disgust! (age 3 disgust of course) But should i care? It is my house, but her room? It needs to also go with turquoise and white and kind of fit in with their Fabler blind. So picture this with two white single beds or bunkbeds (eventually maybe?)

Here goes...take a good look!

Both  Lulu and Nat

 Or

Clouds from Little Baby Company which could then match with

Or go with the Fabler to match the blinds?

 

 Or this one from Marks and Spencer (couldn't get a pic big enough to show)

OR just plain white?

HELP!

Or does anyone else know the perfect thing i'm looking for?