My dd also still got runs/cough/occasional vomit and no appetite after having vomited non stop for 2 days...she's 11 months. She seemed herself, playing etc, for the first few days then got very tired and lethargic - took her to GP, got reassured - and now she's very very slowly on the mend. I think.
I keep a very close eye on breathing, because she nearly died of bronchiolitis at 4 weeks - without a temp, with just cold symptoms but lots of vomiting. And six hours before she was whisked into HDU she was BFing and alert. So I spend a lot of time, seeing as she's had about six bugs already this winter, wondering whether its serious or not
My rule of thumb is, if she's playing and seems bright, I might take her to GP for a cough or small wheeze, but I dont' worry too much.
If I'm worried about dehydration, ie if she's not crying tears/wetting nappies/her fingernails don't turn pink fast after being squeezed - I'd take her to hospital, or to GP if not too bad.
If she's recessing (ribs pulling in) or wheezing a lot, I'd take her to hospital or call an ambulance.
Hate, hate, hate these bugs (doesn't help that I've got one now!) and wish all your LOs better soon, preferably without hospital visits.