Instead, use a firm, flat mattress with no soft bedding underneath. Babies should be put to sleep on their backs to reduce the risk of sudden infant death syndrome. Baby walkers are responsible for countless injuries, and not just in homes where stairs are involved. Put window blinds and curtain cords out of reach. They have been known to cause strangulation when the strings catch on things.
Preschoolers are notorious climbers.
No matter what the children's ages, set the ground rules. Also, show them where they can and cannot go, what cupboards they may go in and which they may not. If you don't want them helping themselves to everything in the refrigerator, put the things you deem appropriate on a lower shelf and give them access to that. Make sure your smoke detectors work, and keep matches and lighters hidden away. If there are any firearms in the home, make sure they are unloaded and the bullets are in a separate container, locked.