I don't know how old the children are, as it makes a difference. I was told to answer each question factually and keep it short. My DD's wonderful godfather committed suicide, unexpectedly due to a sudden and tragic change in circumstances, and I had to explain to a 20mth old that he was dead - he was with us on holiday only 6 days before. I chose not to explain the suicide at that point, instead I said he was dead, I explained why; why couldn't the ambulance help / why didn't the doctors make him better, again I explained very briefly. But I answered each question honestly, even if it was a very brief response and deliberately left out the word "suicide". (I said he fell off a cliff). We were soon on to where he had gone ..... he was an atheist! I told her I didn't know, but I liked to think he had a surprise and was in heaven. Where's heaven, I don't know but I like to think it is in the stars.
Post explanation I never spoke about it to her unless she asked. But I did talk about him when appropriate - eg toys or books he had given her. She did however have a good grip on the idea that death is sad - eg she saw a dead bird, she told my mother that it was dead, it is sad when someone dies. X died and I loved him very much. Some adults thought it was very inappropriate that she was saying this aged 2 -3, I think because of the stigma of suicide. I gather though it is quite normal and healthy and it didn't worry me as she was only saying things in appropriate contexts and very infrequently.
We have since talked about it (aged 4 / 5) and it is a difficult thing to explain. It is though easier to talk about it a few months or years later, as your own emotions are less raw. I told her that you don't want to die, but you want to escape the problems / feelings which are so overwhelming you can't see a choice. He thought he was doing the right thing, even if really he wasn't. I also told her that there are people who help people who feel like that, and if you ever feel sad you should talk to someone as there is always someone who cares.
Winston's Wish is great - there is also another charity which specialises in bereaved parents in the South of England which is very helpful.
Hugs & sympathy.