I have not read all the suggestions in details by other members, BUT THE TRIAC IDEA IS THE DEFINITELY DANGEROUS!!
Let me explain, triac have no inherent isolation, relays do. As a student you may not be conversant with concepts of isolation and safety. So triacs will make you project unsafe/ hazardous. Besides relays can survive abuse better than triacs, like a shorted load. Isolated triacs called solid state relays are expensive. If you use base mounted (plug in) relays with wired connections(a.k.a. rail mounted relays) you will have safety with a simpler mechanical design. And relays are very easy to drive.