I think the way you just said it works well. You are sad because the babies you had in your tummy are gone now (whether they are in heaven playing with God etc...) and it makes you really sad. Assure them they make you happy and they and your husband will get through all of this because you love each other. Just let them know you may have tears because you still miss the babies. Kids are so smart, loving and forgiving-they will understand! Only time will make your tears less and less. One day at a time, ok. Talk with friends and family (make time). My thoughts and prayers are with you. Sorry for your loss.
First, I am so very sorry for your losses. I know it's the hardest thing parents will ever have to go through. I have been through 2 miscarriages and lost my 10 month old son 4 months ago to a rare liver disease. I can tell you, with time, it gets just a little bit easier. (I didn't believe it at first, but I am starting to now) At times, I cry and just think about my son, and sometimes I can't stop crying. It's all a part of the grieving process, and you need to get it out and be able to talk to someone about it. I have a very close friend that I talk to and trust, and anytime I am sad, I just call her or email her and she always knows just what to say.
I have a 2 1/2 year old and he knows what happened and we told him the entire story. We talk about his brother every single day and he understand some things. I try not to cry in front of him, but sometimes he says the sweetest things about his brother and how he misses his best bud, then he looks at me while I am crying and gives me a big hug and asks if I am sad. I again just explain how I miss him, but that he is Heaven now.
For me, having my 2 1/2 year old has helped tremendously because he makes me keep going. I have to take care of him and love him, and he always helps me and is so sweet.
When you are ready, sit down with the kids and explain what happened, so they know why mommy cries at times. If anything, they will just want to hug you and kiss you, and ask questions.
The best thing you can do is keep yourself surrounded by others, even if it's just your children. I find, when I am alone, is when my mind wanders and I lose it.
Just know, with time, you will heal more. You will never forget it or be completely healed from it, but it will get just a little bit better in time.
I have a friend who just went through her 5th miscarriage, and each time, they planted a tree or did something special in their garden to remember them. I think that is a sweet thing to do. If you ever need to talk, you can always message me. I am so sorry you have to go through this. (((hugs)))