Here's a bit of advice from me. It's the same sort of self talk I give myself when needed. Perhaps you may find it useful.
1) You are enough.
I know you may feel like you're not adequately planned or prepared or ready. You may not feel equipped. You may feel frustrated that you did not sign up for this. Put all those worries aside. You have what it takes to do a good job because you love these kids so much that you are willing to give it your best. You are enough.
2) Atmosphere is important.
It matters less how much you accomplish in a day, it matters more how you accomplish it. Think less about the end goal. Think more about the process of discovering, enjoying and connecting with one another. If not everything gets done today, that's okay. There is tomorrow. Keeping the atmosphere of the home peaceful is a more important than accomplishing the list.
3) Do everyday.
Read everyday. Read to the them, regardless of their age.
Go outside everyday. Explore with them, regardless of their age.
Consistently doing these two things helps establish a connection with one another and joy in learning. It often makes it more likely that other things on the list will be checked off with greater ease as well.
4) Give yourself grace.
This whole homeschooling thing is new to everyone. It may go well at some moments and others it may not. One step at a time. Give yourself grace. These weeks of schooling at home will be forever memorable to your children. Keep working at making this experience a time together you will both forever treasure. You can do this!