Make Health a property of the Enemy family, so instead of having GuardHealth or GoblinHealth, you just have Enemy.Health.
Add another Family instance variable called "attackfunction". Let that variable contain the name of a function, like "EnemyAttackFunction". then you can make an attack function with that name, That lets you have one main attack function that everything in the family defaults to, but you can still use a different function for special cases.
If you are interested in learning more, read up on something called polymorphism, which is an important concept in programming, even in Construct 2. Also, as always, feel free to ask questions ^_^