For small children the most important consideration should be that it be comfortable to wear. The situation is already strange and uncomfortable enough for them without their clothes adding to the problem.
For older children you can think of something more formal; but it doesn't have to be dress suits and ties.
Teens will probably want to dress as adults.
black or white
No. It is disrespectful and not the place to wear them. A funeral is like church where you wear an appropriate outfit.
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normal clothes that they wear
If your children were close with their father you should attend the funeral to be there to support your children.
everyone gathered at his Funeral. funeral is to respect the dead.
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yes
black clothes
well it depends in wich religion you are so for example i could wear any color in a funeral but if you fell that you can wear any color you can
In some countries, you should. In Sweden, the closest relatives to the deceased traditionally wear a white tie. That is, children, parents, husband, wife or siblings. Others traditionally wear black tie.
yes