House oriented North-South. How do I warm the northern bedrooms?

I have a cinder block house, oriented North-South. It's 14x50 with a 10-degree lean-to metal roof facing West. I had no control in how it was built. The main bedroom is on the south side and is quite nice in the winter. However, my kids are on the north end and their rooms are ice boxes. So much that they refuse to sleep in there after Thanksgiving. The cinder blocks stay cold no matter how warm the air is inside. How can I transfer some warmth to the other end of such a long building?

This reminds me of heat the person not the space.

Using micro-heaters:

https://permies.com/t/131936/cut-electric-heat-bill-microheaters

https://richsoil.com/electric-heat.jsp

The only other solution I can think of is open the curtain in the afternoon to take advantage of the suns warms.

This is an area I have worked in, I may be able to help.
But I have a lot of questions first.
- Is the floor on a slab or stumps?
- do your windows have pelmets?
- have you sealed all draughts?
- Is the ceiling insulated?
- What heating do you usein the house?
- Could the external walls in those bedrooms have a wardrobe built on them?
- Could those same walls have an insulating blanket fitted to them?
- Can the roof sheets be removed and the insulation improved?

John has asked so great question which the answer might help other folks make some suggestion.

Other than the micro-heaters, sleeping bags made for sub-zero weather might help.

Years ago when I had a newborn, the electricity went out during a snow storm.

I put my toddler son, myself and the newborn in a sleeping bag to stay warm.

In addition of JCDs questions: Do you own the house; how big in the kids’ bedroom; do you have access to the attic?

A basic first step is to hang quilts, heavy lined drapes, or similar on the walls.  

Consider setting a box fan in the doorway of the bedroom blowing into it.

If you do have access to the attic, add insulation above the bedroom. Also consider duct work from a warm Area of the house to the bedroom with a fan to push the warm air.

If you do own the house, and have the funds, the best solution for me would be to add exterior walls around the bedroom with insulation….keeping the concrete block mass inside. This approach is greatly impacted by your roof overhang.

 As a retired designer of passive solar and highly energy efficient homes, remodelings, and additions, I have to commend the posts so far.  This is a smart group ;O).  What i can add is maybe a bit of prioritization.   We don't know what climate you are in......only that it gets cold.  In the long run, insulation on the outside of the block, and in the attic, would be ideal, but interior insulation would be good as well, since thermal mass in that location doesn't really do much that is effective, and might even extend summer overheating, from west wall sun exposure, which might be mitigated with plantings/shading or even sun reflective paint..  For now, you need to make the walls not fell so cold. So, as was already recommended, do what they used to do in stone castles, and hang cloth or blankets over the walls, to present a warmer surface and reduce radiant heat losses from the people and objects in the room.  Raising the average temperatures of the exposed surfaces, is roughly 40% more effective than raising the temperature of the room air.  Of course, seal any noticeable air leaks, too. Then leave the door open and use a box/floor fan to draw cold air out of the room, so that warm air will flow in through the top of the doorway. Having the fan blow out of the room (besides not creating a cooling breeze in the room) will work with the natural air flow instead of again it.  Of course, warmer bedding is always a good thing.  Get the kids involved in figuring out and solving their own problem, too.