Texting is ok IMO. It shows you are thinking about them but it means they are not pressured into talking to you.
When my DD was terminal people suddenly started phoning. It was relentless. Every five minutes. I know that people wanted to show support and that they cared but it was too much to deal with. I bought an answering machine. I could listen to the messages without having to talk. I would very much recommend this to anyone in this horrible situation.
They will need you to be around for a long time. Support drops off as people have to go on with their own lives. It is very lonely being a bereaved parent. Its hard to beleive but people really do avoid you. You feel like a freak.
Keep in touch. Dont make demands, if you offer to do something make sure they know its a sincere offer. Make specific offers rather than 'if there is anything I can do'. Let them talk about their child as much as they want. Dont say 'oh dont cry' or 'please dont get upset'.
I am not implying that you would do these things or even that they are nasty things to do. Just talking from experience.
Our DS was 3 when DD died. You cant really explain death to a 3 year old. They dont understand. DS is still confused now he is 6 although we have always been open and honest with him. Just recently realised he thought cancer is a person who stabbed his sister
Be honest and give short answers to questions as they arise. We talk about heaven because thats what we believe but I know thats not for everyone. Avoid fuzzy language like 'gone to sleep' that can terrify a child. Talk about how sad it is and how sad the LO's parent are. Be prepared for questions at odd times.
I am so very sorry that your friends are having to cope with this. Its a terrible, horrible tradgedy.
I am sorry.