D.L.
Don't EVER tell a child the person "went away"!!! I was told this bout my mother at 2 (almost 3) yrs old. I felt I needed to be perfect for years otherwise others would "go away" too. Until I got teased on the playground in 1st grade and found out the truth. My family did the best they could (close to 50 years ago) in the circumstances but it still was wrong and caused problems. To this day, when I here those words "went away", I literally panic.
I always told my kids that the person's body was so ill and worn (I used those words as I never use them anywhere else cuz maybe I get sick or tired and dont want them to panic) that they needed to go home to God in Heaven. Period. Thats it. Then a few months later, they would ask bout the person and I'd repeat myself but they would usually ask how or something similar. I'd add a bit more info then. Each time they would ask for more I'd tell them more.
Children under 5 will accept the truth easily and wont doubt you a bit. Also allow yourself to feel what you feel and not hide it from your children. Sometimes you will cry but sometimes you may laugh and they need to know that its all ok. Each person mourns and goes thru the stages of mourning differently. Dont deny anything.
My son who is a teen, has been to more'n a dozen funerals. Some people close to him; his grandmother and grandfather included. Sometimes he cried, sometimes he told funny stories bout the person and sometimes he said and did nothing. He knows how to deal with his grief in a way that works well for him.