Honestly, the house just seems soulless. Sorry.
There is zero curb appeal, it just looks like a box. You need to address that before you do anything else in my opinion.
Kitchen
Cons - Very bland, cream walls, cream units, cream range etc. The only colour is the green stools which honestly are not a nice colour. Brighten it up, find a way to add colour that is pleasant and not in your face like those stools.
Pros - its a massive space, great unit layout
Lounge
Cons - ever heard of red and green should never be seen?? The sofa and greens clash. It is a big space but poorly laid out so just seems soulless and devoid of warmth
Pros - its a huge space...
Room with shelving
Am assuming this is the potential 4th bedroom?
Cons - it is full of clutter, its the only room that looks used. Clear it up, tidy it, make better use of the space
Bedrooms
All lovely. Yes the third one is small but you have made good use of it.
Bathrooms
Family homes would expect the bathroom to be upstairs. I have a downstairs bathroom and love it but I do get it outs a lot of people off. Is there any way to remodel or at least get quotes to make the master smaller and have a shower fitted in the toilet upstairs?
Garden
Needs better pictures
What is the rubbish pile by the trampoline? The picture isn't clear but it looks a mess. Get it tidied up.
The whole house seems really cold. There is nothing "family home" about it. Its cold, white and overly clinical. Have a look on Pinterest for ideas on how to dress rooms...flowers, pictures (but not loads).
It also seems a really high price for what is there. In the same price bracket there are some much bigger houses with better layouts. Technically yours is only 3 bed so I would guess it is at least 25k over priced