In the same boat! 2 boys and a girl, oldest is 6, youngest is 9 months. 3 has been so hard, don't think I could go for 4 but always curious what others say.

I find that picking out clothes the night before is very helpful and laying them out for our 6 year old. He has started to initiate picking out his clothes now and putting them on by himself. It started with small steps. Also, depends on how easy clothes are for them to get in the closet/drawers. If it is a challenging process for them, it will make independence more difficult. I would start with small and work your way up. And followed his lead on things and didn't force it or make it seem like a chore.