If you need to activate a 12VDC Relay, you does not need any analog output, just a simple digital outputport…If you want to avoid electronic first, I suggest to have a look ont the several modules provided by GHI, in particular :
http://www.ghielectronics.com/catalog/product/315 => This one will drive one of your several motors (Up to 40V and 3A to check with your team)
http://www.ghielectronics.com/catalog/product/327 => This one to command the relays.
Then, when you will have validate thoses modules, all the schematic are open source so that you’ll probably fin an independant electronic guy to build a board for you without spending to much money !
To answer your question, it’s often convinient to use at least a protection circuit between the PIN OUT and the relay, that also enable to put the right voltage in the relay without impacting the output (optocoupler, transistor and so on…). But really, I engage you in buying a gadgeteer board and some module to have test !
When can help you choosing the right one !