I found this idea on Pinterest:
This was so much fun! The glow sticks were a gift from Grand Aunt Pam. (thank you!) I’d saved most of them for a ‘rainy day’. I told the kids I was making them a surprise bath, but I didn’t show them the glow sticks. I said they needed to wait in the hall while the tub filled. So there was anticipation. I ran the water, and added just a little of my favorite bubble bath. (Mustela of course!)
Then, when I’d broken the sticks, given them a shake, and tossed them in the warm water, I turned off the lights and opened the door.
I said, “Come in to the see the bath tub!” They Loved it! They Oohed and aww’d. I lit a couple of tea light candles for extra ambiance, but kept the lights off. It was great. The kids would not leave the tub! I had to fill the bath with more hot water because they were in there so long.