I'm having my c-section in 17 days and am constantly tired! I also have a 3 1/2 year old son, so I know how hard it can be. I'm SUCH a clean freak I'll clean until I'm exhausted and can barely walk, and it's soo tiring. I would just try to do one room a day, maybe after your toddler falls alseep (try to get him to bed earlier, or put on a movie for him before bed) and don't overdo it. I'm going to go on one last cleaning spurt right before she gets here so I don't have to worry about cleaning when I get home, but at this point getting as much sleep and relaxation as you can before you're out for a few weeks is the best idea!
Just take it easy. Maybe call a close relative or close friend and ask for a little help? It's not a bad thing to ask for help especially when you are preparing to give birth! I know that if I were in your shoes I would be trying to take it easy these last few days because you will be tired afterwards! Good luck mama!