What is the safest wood perservative to use on cedar wood, in a daycare playground? It will be used

Forts, benches, playhouse and climbers.

What is the safest wood perservative to use on cedar wood, in a daycare playground? It will be used on:?ballet theater

Nothing! Cedar is a naturally self preserving wood and should need no treatment for many years. Then if you must, use a natural vegatable oil orpeanut, olive, canolla, etc. and spray liberally on the cedar and wipe down any excess with a cloth.

What is the safest wood perservative to use on cedar wood, in a daycare playground? It will be used on:?chicago theater opera theater

75% boiled linseed oil 25% turpintine

Both natural organic compounds
Whereas western red cedar does have excellent natural weather resistance, you should follow the answer using linseed oil. If not, it will not take long at all (a matter of months) before the cedar loses its beautiful red color and turns grey.
Use answer 1, and do coat it. Cedar is not impervious to decay. I had a 16 x 32 deck made of red cedar, lasted about 15 years and then almost weekly, entire boards would disenigrate--I don't plan to use it again when rebuilding my deck, will go with treated wood and a water repellent to boot. Water is the chief enemy.