1. Separate the breakable ornaments from the non-breakable ornaments.
2. Give the non-breakable ornaments to the toddler to keep them occupied/distracted while you put up the breakable ones.
3. Intermittently, coerce the toddler to put up some of the non-breakable ornaments. Partially succeed.
4. Ask the toddler to "stand pretty" in front of the tree for a picture...with the intent to see how tall they are in comparison to avoid accidental knocking off of ornaments.

5. Then ask them to stand tall and reach the sky. Unsuccessfully. Chase them around the room and hold their arms up tall next to the tree.
6. Indicate "reaching height" with a ribbon.
7. Finish decorating tree's upper portion, making sure anything you don't want to be touched is above the ribbon.
8. Watch the toddler have a cow when she sees a pretty ornament that she cannot touch go out of reach.
9. Decorate below the ribbon with non-breakable items a.k.a. things the toddler can take off at will without being hugely reprimanded, or that her baby sister can pull off and stick in mouth without horrible side effects.
10. Admire the "split level" Christmas tree, and hope Grandma approves when she gets home.