Having taught primary and secondary school children ,they find the use of "gone to sleep" and "passed away" confusing ,and little kids find going to sleep worrying as they think that's what happens,and they worry about it!
And they think if they ,mum ,dad,go to sleep ,they won't wake up,but it depends what makes you feel okay,my husband died age 30 and I used the word died.
Our daughter was nearly five so I told her that daddy had gone to be a twinkle star,and when she was a little older I explained what that meant.
There is no right or wrong ,died is a blunt word,it's very final,and passed sounds gentle.
I am a medium and always use the word pass,to people I read for,but spirit uses the word dead,
It's such a horrific thing to go through ,the words are all meaning the same.
We in this country are really uncomfortable about saying anything about death,and really do drop you or cross the road.this has happened to me.
In Europe it's much more open ,the morning is open,feelings and tears are open and very much natural.
Hen visiting Spain,I was asked where my husband was when visiting with my daughter,I said Ma Marido est muerte, simply my husband has died,and a plethora of black scarved grannies came out. To pat my hand ,cry with me,wring their hands a bit,it was strangely refreshing!
Use the words that you can cope with, for me ,I felt passed and fell asleep where not right for me.