Should a 2/3 year old see his mother's dead body at her funeral to help understand better or would that do more harm than good ?

Depends on the child: Generally not a good idea but some children are spiritually aware and may ask to see. At 2-3 they do not really understand death....And won't.. You may want to call a grief counselor and ask their opinion as well...Mom is not coming home whether child sees the body or not. Pictures may be more helpful..Having a an album that you can show the child pictures of mom regularly.

Possibly: Even 2-3 yo will have a concept of death, be it crude, and a brief viewing may help prevent issues of abandonment later. A close family member or friend that can focus on reading the reaction of the kid and leaving quickly if needed helps.Those dealing with their own grief may be less able to assist the kid.A funeral would be too much at this age.