This time of year is often much darker anyway, as the shadows are longer. You might find it gets a bit brighter as the sun gets higher in the sky, unless it is literally due North and there is no light coming in at all.
In which case, yes, definitely knock through to get the South light into the house.
Work out where the light is coming from on both sides and reconfigure accordingly/put sky light in etc.
Another idea is to make the windows in the kitchen larger? A possibility if there is only the traditional sink under window arrangement, rather than a big expanse of windows/french doors.
Or you could reconfigure the kitchen entirely so that the table is at the light end, and the kitchen bit, with task lighting is at the other end of the room.
I like rooms which aren't knocked through, but a poky front room with all the sunlight is slightly pointless, when you have acres of space in comparative darkness, and you are of course going to spend an awful lot of time in the kitchen, especially with kids.
Another alternative, which my DSIS had in her house, was to put table in the front room and make it a nice dining room, and put the sofa and telly in the middle room onto the kitchen, quite sociable really, as most of the evening is spent in the sofa room so it didn't need to be that light, whereas meals are better in bright room.