Vaccines are still shown to reduce risk of hospitalization and death even with omicron. So, if everyone is going to get it, wouldn't you rather be more protected when you get it?
The risk of hospitalization for children is virtually zero. The risk of hospitalization for healthy people under 50 is miniscule.
Risk of hospitalization for children aged < 5 years with Omicron is quite a bit higher than previous variants. Take a look at the CDC data, compare age groups this year vs. one year earlier.
This trend exists because children are being tested for COVID after being admitted to the hospital for entirely unrelated issues (broken bones, etc). They're in the hospital _with_ COVID, not in the hospital _because_ of COVID.