You have children and it's a family house but have no downstairs wc, which is absolutely essential and something buyers will expect in a family house.
On looking at your kitchen, it's quite a large space and you could try drawing out how to reconfigure it in different layouts. You could do this in the actual space by marking it out on the floor using a powder spray or coloured string, and placing chairs or items of furniture, or buy some squared paper and draw it to scale. When I was doing a kitchen plan I bought some large flipchart sheets to measure out and mark everything on it. Or you may be a whiz at online drawing.
You don't actually need a very large kitchen space once you have those other great facilities, the wc, utility, shower and cloakroom - which don't require a massive space either. You would put them down in the bottom left corner, underneath the bathroom convenient to where all the plumbing already is. You have nearly 20' across the back wall which is more than enough to play with. Ideally you would keep your side door access - it's a great thing to have, especially for a family house, and I would think twice or three, no, ten or twenty times before giving it up - and enter into a small lobby with hanging space or cupboard for coats and boots and brollies, leading to a utility room - big enough for washing machine, sink, clothesline above or airer on floor; if you wish, a tumble drier could be set atop a washing machine - utility room can actually be a small space - leading to a shower, wc and basin room - which again can be fairly compact. Or you can combine laundry and wc and shower in one room as some people do, though I don't think it's ideal. Should also mention you can get compact showers and sanitary ware designed for small spaces.
In the kitchen you just need cupboard and work space, cooking, washing, dishwasher, fridge and table and seating for dining. You have a long wall of 15' down one side in which you could have all the cupboards, fridge, dishwasher sink, cooker and workspace in one run and in the rest of the space a large table and chairs, or perhaps, continue your workspace around the corner to the wall with the living room. Or you could use that wall, along the living room, to put in banquette seating and table and chairs, which would take up less of the space than table and chairs in the middle of the room. That could combine with a smallish island if you want one, out towards the garden. You could have a movable island if you might want at some point to change things around. You would put your larder along the back outside wall so that you can ventilate it to the outside to keep it naturally cool and dry. That's the beauty of it.
I would get drawing, exploring and weighing up possibilities for the existing space before you jump into some massive building project.