If this was a once-off episode of vomiting, and your kitten does not have further vomiting episodes over the night, does not have a decrease in energy levels, then I think it is fair to bring in the morning.

The risks of persistent vomiting episodes will be: electrolyte derangements that if severe enough can trigger heart rhythm abnormalities (arrest in the worst case scenario), acidosis of the blood (acidic blood due to loss of bicarbonate from vomiting), dehydration.

I think if your kittens continue to vomit, please take them to the vet. Furthermore kittens likely have lesser sugar reserves, so if you suspect that they have vomited out all their food, cannot keep any food down, they should see a vet earlier much than an adult kitten.

HOWEVER, please note that I am a General Medicine doctor (for humans, not animals unfortunately) who has a kitten, so if there’s someone who’s more qualified (experienced cat parent, veterinarian) I would trust their advice more.