M.G.
P., I am so sorry you and your family are going through this.
Keep in mind that your kids will say things about not wanting to move because they like their house, neighbors, etc. When we moved my kids said they liked the old house better that they missed the neighbor (who was a 75 yr old man they were afraid of when we lived next to him). Don't let it get to you. I acknowledged how they felt and told them that I really liked our old house too but I really liked our new one just as much. Have them be part of the packing, unpacking and organizing their rooms it could help them be excited.
You said you have already contacted your church, that's great. Don't be afraid to be specific with the type of help you need whether it be financial, emotional or physical help. I'm sure the paster or minister would help organize church members to help with the physical moving if you tell him/her that's what you need. I know our church helps those in financial need too, just ask.
For boxes start asking around to see if anyone know someone who has recently moved and still has their moving boxes. We got a ton of boxes that way, it was a friend of a friend. Ask all the parents at school if they know someone who has boxes. Start spreading the word now so you aren't scrabbling at the last minute.
You and your family are in my prayers.