You should move the kids' stuff out of sight for viewings.
The decor you have does not go with children's stuff from a visual pov. Children's toys also clutter and distract. You want people to see basically what they see in the photos. You want to enable them to see the space and imagine their own furniture there, and possibly imagine their own lifestyle there too - it might not be one that involves children, and if it does, then a living room that is dominated by a large tent or other toys might be offputting. That is the downside of open plan - one little thing out of place and your home looks like a tip. I have always lived in open plan homes myself, with children, and I like it. However, there are people who like to shut a door on a playroom and your house doesn't need to remind them during viewings of why they might hesitate to buy an open plan home.
Yes, it is your home, but it is a property on the market too, and for a few weeks you can tidy up when you know people will be viewing. You need to prioritise selling until the house sells. When you move into your next home you can let your hair down.
The problem with the decor is that it looks clinical, not that your house is actually physically cold.
If you could find a few large pots with a rugged, not metallic, and not angular appearance, and put in some really large houseplants you would soften the angles a bit. Put a fern or medium sized ivy in a pot on your kitchen counter. Or a medium sized pot of succulents, which are very 'in' right now. Maybe throw a blooming plant or two into the mix. It's about softening the lines and also introducing a little more colour but not too much.
s-media-cache-ak0.pinimg.com/736x/5b/a9/7c/5ba97c1cc0bd5a9f2c85342dda8a9668.jpg The basket brings texture here.
A few of these would introduce a natural, homespun element into your decor. It would balance it a bit and suggest to buyers that an alternative decor would suit the space too.
You could buy the plants in plain plastic pots and put them in tall baskets, pot and all.
Maybe include tradesman owner as part of the description.