Moving out of grandmas house with a 2.5 year old

So the time has finally come to leave my moms house. She was generous enough to let me and my husband move back in when I got pregnant with my first so I could afford to be a stay at home mom. She’s now 2.5 and we had a little surprise baby who is now 5 months old. It’s time to leave as it’s just way too cramped for all of us and I know she would love to have her house back.... we found a place and move in December 31st. My 2.5 year old is incredibly attached to her grandma (my mom) and knows nothing but here. I’m so worried this is going to be a terrible transition and she’s going to be sad and confused. Any tips on how I can make this easier for her? ☹️