Cleaning king-sized bedspread my toddler vomited on

You didn't mention what the comforter is made of, as it will make some difference. We have a super puffy king size down comforter, and the cat has taken a liking to pee and poop on it, so I would say I have some experience! Next time it happens, make sure you wipe up and soak up what you can, and treat the spot with some kind of enzymatic cleaner that they sell for pets, the type that says it naturally takes care of smells (we use "Nature's Miracle"). Then drive that thing over to a laundromat, stick it in the biggest washer and dryer that you can. Make sure it is fully dry, especially if it is down. After it is clean, setting it in the sun helps take care of any residue smells. Don't try to wash it at home because you can't dry it properly in your home dryer, and it is disgusting to lug a wet and dripping comforter to a commercial laundromat (I've tried it, don't recommend it). Some laundromats do wash and dry if you don't want to wait for it.

I also have a king size bed and had my dog get sick all over it.  I took it to the nearest laundromat and put in one of the larger washing machines with plenty of Tide.  It got is very clean.  Takes time, but it does work.

Laundromats will have large-capacity washers and dryers.

Laundromats often have large-capacity washers. Try using the largest washing machine available at a laundromat.

You can send it out to be dry-cleaned, but somehow that seems less sanitary and then you have dry-cleaning fumes and residual chemicals.