I really really don't like toilets opening off of the kitchen. Especially a kitchen diner! But that could be solved by moving/adding a door.
It's nice and bright in the pictures, I'd want to check it's really like that.
I wouldn't put DC in the bathroom bedroom, too much chance of them getting up to mischief when you think they're 'playing in their room'!
I would consider putting a wall in across the entrance room right at the foot of the stairs (orange line) or even a glazed partition to keep the light, to give you a porch/hall area, and stop drafts from the door/stairs. You could then put in some understairs storage for the living room. At the moment it's a nice open space, but there's nowhere to put anything!
Would you need to use the garage for parking or could you put some doors in the back/side and use it as a play room / garden room or something?