Starry nights vs Night prowl with 8 & 10 yrs old? Which is better?
Any other night activities? Bon fire?
Check the current Yosemite Guide newspaper.
Bonfire? In these conditions? Fire danger is high.
You have only asked questions here on the Yosemite forum and haven't shared anything about where you have chosen to stay or what you're planning to do. Can you give us some additional information so we can give you relevant replies? For example, I might suggest a hike or stroll, or a moonlight 'picnic', or a campground ranger program, or another free program.
Heads up wee wild ones is not a ranger program but still with a great naturalist. There is a ranger led Jr ranger campfire on Wed, Fri, Sat nights at least through August at 7pm. Head to shuttle stop 16 and then head straight back from the bus stop to the sign for the fen... Head through there to the campfire ring. Bring marshmallows and sticks for after the program (not during) and you can roast marshmallows.
All of these options are great. Jr ranger campfire and wee wild ones are free.