Here are a couple moore ideas. I like that the brightly colored collection adds to the decor in the first one. The second one is great if you have room to hang them in on the rod. Simple shower curtain rings would do the trick.

None of the above - I love prairie, desert or mountain scapes. The water photos are too "cold" looking (I've experienced both - I still feel chilled when I think of it), the mossy forest is a bit creepy (beautiful but creepy) and I'm not fond of having humans on my wall - even if it is as minimal as a child's hand holding a dandelion (the sky in that photo is to "cold" looking - like a cold fall day). That's just me. They are all great photos. Just not my style.

You say the kids come in the small door and then bring their stuff to the large door to drop it? I think the "mudroom" needs to be at the small door. Anyone who brings their stuff out of that area has to clean the glass doors next time they need it. As for the guest entry, you need to get something bigger than that desk, and your picture needs to be lowered so the center point of it is 5' above the floor (you'll have to calculate the centimeters.) Consider making the investment to reverse the swing of the door so you can make the best of the larger wall to greet your guests with a console or credenza and some decor.

Get the professional sander guys in to repair the living areas and kitchen but don't go too dark with the stain as it will kill the lovely grain in the matai. I'm thinking a couple of tones richer than the timber knots showing in your photo, definitely no yellow tone at all. In NZ stepping on to carpet especially in a kiwi winter is so much nicer than a cold floor board shock!!! A nice area rug for the lounge and you're done.