I always get on the plane and change straightaway into the PJ's. And get comfortable. Though I always keep a t-shirt on underneath the PJ top as I find the label of the PJ scratches me and is really uncomfortable.
The locker is plenty big enough to hold your shoes and also hang your clothing. But I have never been told I can't put my shoes in the seating area? I usually just chuck them underneath the small opposing seat.
What you need to understand is that this is First. You can tell them exactly how you want to be served - whether that is together or separately. You tell when what and when you want to eat.
You could have a desert just after take off, 2 hours later have a main meal and then just before landing have the starter. It is food on demand and for me this is the reason why First so so good. This food when I want to eat it really helps with combating jetlag.
I never get disturbed by other people eating when they want - so I wouldn't worry about it.