Welcome to the forums. No cheat the I know of for that. If one is a ghost and one a sim, it's about a 50/50 chance the child will be a ghost. The only way to have a 100% ghost is if both parents are ghosts. Or, if you have generations you can make and drink the ghost potion, make the sim into a ghost for awhile than try for baby. That should make it 100%. And yes, it's apples for boys and watermelons for girls. Eat at least 10 of them.