Warning, long post..but please bear with me as I need your help!

We moved into this 70s/80's bungalow last year (we are in the UK)
We are installing a new wood burning stove in our living room, which is 6m x 10m with large dual-aspect windows/patio doors at each shorter end (north/south). The chimney breast in in the centre of the long wall and so this is where the stove will go. The main entrance to the room is slightly off centre with the fire place (this in itself drives me mad, design wise!) I just can't get to grips with how this room should look, at all.

As we are doing a degree of knocking out and re-plastering anyway to do this we are considering whether there is any further remodelling we should do at the same time so as to minimise the amount of disruption in future years and also have a space that works for us long term. We currently have 2 small children (3 and 18m)

We have a dining room (currently a play room) that is adjoined to the living room with a (70s looking) glass "box" on the north aspect of the house and I cannot decide whether or not to remove the partition and have a very large open plan L shaped room.

The other reason for considering this now is that we would need a larger stove if we make the room larger.

The benefits of opening it up would be:

1) to create a flowing and flexible space with different zones. (Dining, Socialising, TV watching/kids play) We would have two distinct sitting areas on the north/garden facing side of the room, one for relaxing watching tv, and one directed away from the tv. (At the moment we have all our furniture at one end of the living room and nothing but the tv and a couple of chairs at the other, with the fire in between, and the off-centre door splitting the space in a clunky way.

2) to create a dining space larger than the current dining room can accommodate

3) to freshen up and lose the 70s feel of the glass box room, (this is a bugbear of mine)

The negatives or my key design questions regarding open plan spaces would be:
1) Potential for mess to spread across all living areas with no easy containment. Is this really a big problem?
2) Does a dining table in the open living space work? Does it make a living room space look cluttered Or can it still maintain a "calm feel? Or, is it better to have it tucked away in a separate dining room?
3) I am concerned about the room potentially becoming too big and "cold" feeling. I need some design ideas to help the roomy feel permanently welcoming and "cosy" despite the size.
4) Floor covering - we love wood, but again unsure if this will make a large space "colder". Can add rugs, but is it better to have carpet?

I will attach some photos I took today. The rooms are not usually so messy but we had toddler guests over to play. This in itself shows one of my main concerns.

I should say, despite all these worries, I still really want to do it, but i'm worried about making a costly mistake too!!!