On their first day to the grand canyon, the family took half as many photos as the ones they have in the gallery, meaning they took 1/2*400 = <<400/2=200>>200 photos.
The total number of photos if they add the ones they took on the first day to the family's gallery is 400+200 = <<400+200=600>>600
On the second day, they took 120 more photos than they took on the first day, a total of 200+120 = <<200+120=320>>320 photos.
After adding the photos they took on the second day to the galley, the number of photos will be 600+320 = <<600+320=920>>920
#### 920