Is viral pneumonia more dangerous for the elderly children?

Generally: It depends on the virus - there are outbreaks where the old and very young appear to have been spared for unclear reasons while those in the prime of life are most affected (e.g. The h1n1 outbreak). In most cases, however, the very young and elderly are more vulnerable due to either a fading immune system or an immature one.

Yes: Both children and elderly have poor immune systems. That's why we recommend the flu vaccine every year to them. Most antivirals don't work if not started the same day of the beginning of the disease. Viral pneumonias do not respond to antibiotics and seldom respond to antivirals.