To secure your cabinets, the big options are usually an interior latch that you screw into your cabinets or an external lock. Each have their drawbacks, with the big problem with internal latches being that they often stop working. The downside of an external lock is that you have to remember to put them back on each time you open your cabinets.
To be extra safe, you might use a 'layers of protection' childproofing method and install both.
