I'm so sorry for loosing Matthew, I've been thinking of you and your family and praying for you all.
allow yourselves to grieve however long it takes.
cry, scream if you need to. cuddle your kids and hubby
talk about it and keep talking about it
write a diary
keep whatever he wore or was wrapped in near you
remember to explain to kids you are not mad at them (my kids used to get worried, they thought they did something wrong)
in fact what helped me most was answering any questions my children had and talking to them.
even if it broke my heart the sweetest thing they said was that they missed her and wished she could be here playing with them 
the hardest thing apart from right now will be the first "anniversary" of everything that's just happened/will be happening.
and I know you can't imagine it now, but there will be a time when you will be able to think of him without crying
I hope you find these thoughts comforting in some level