The garden is 50ft - it's just they haven't made the most of it. If you take out most of that huge patio and all the gravel to replace them with lawn and swings, then just leave some patio outside the doors to the garden, for a table, chairs, sand pit etc, it will be perfectly big enough for two kids to play in.
I don't much like the layout of the kitchen - wrapped around that central block so even though it's open plan you are often cut off from seeing what DC are up to or from chatting with guests. But it's a great size and I expected it to be a lot more expensive.