Since your kid will be using this bag, there’s no way around it — you’ll have to clean it sometimes. Kids are messy!
But, whenever possible, you should avoid putting your sleeping bag in the washing machine as this will increase the wear and tear on your bag. Before a full wash, consider whether you can spot wash the bag.
Here are the two cleaning methods you can use:
Spot wash: Use a toothbrush, soap, and water to scrub dirty areas such as around the opening of the sleeping bag or any marks. Hold the liner away from the insulation and rinse.
Full clean: Wash your sleeping bag according to the manufacturer’s instructions. Do not use fabric softener, and do not wash it in a top-loading machine with an agitator. Put it on the delicate cycle.