I'm sure it could be done with some relays, perhaps by using 3 relays and wiring their contacts in series so all 3 relays need to be closed before any power can get to the solenoid, but a controller or some kind of PLC like device may be better suited if I wanted to add some extra "security" like maybe having to press one of the buttons 3 times in a row or some weird thing.

It's the concept that's got me interested and thinking of the different things to do with it, because it sounds kind of like automation which is what I went to school for.

If all Grndpndr needs is a simple action, then a simple solution is the most appropriate. However, the above quote seems to indicate that a more complex unlocking sequence is desired. In this case, a microcontroller seems to be the better solution and will allow flexibility in modifying the sequence in the future.

It all depends on the real requirement.

 

I might go with an arduino for the sake of flexibility and that it could be configured/changed on the fly, but I'm going to also look into smart relays as well because it's kind of a combination of a relay and microcontroller.