My daghter lost her twin boys when she was also 21 weeks pregnant, and believe me I fully understand the pain you are going through. However her little boys had already died- i truly cant imagine how much worse it is when your children are born then die some hours later.
Are you from the States then? As over here in the UK, you do not need ot make burial arrangements if you don't want (or indeed not capable) ot make them- rather the hospital will arrange a cremation and your little ones are recorded and remembered in a special garden of rememberence.
Lastly- I know you and your partner are grieving now, but it does get better over time- just got to remember that for whatever reason it wasn't Hannah's time and sometimes, these things aren't meant to be.
I'm not a great religious believer but I sometimes see the state of the world we live in and think that maybe my grandsons are in a far better place afterall- nothing and no one will now case them pain.