DS (3 almost 4) and DD (2.5) share a bedroom (Kura bunkbed). Bedtime is a disaster. Like sh*t show. Here is our routine

Eat dinner (5:30)
Play 6;00-6:30
Brush teeth
Books (around 3) in dim room
7:00 Light out, sound machine on, I sing a few songs

The trouble is they don't fall asleep. We have to sit in the room and basically yell at them.for an hour until they fall asleep. They giggle, rile.each other up, want to get out of bed etc. It's so bad. I don't know how to make it better. I dread bedtime. I hate yelling but I don't know what else to do. Taking away things seems to abstract at night. I'm at such a loss. Help!