wow...sorry for my surprise at your question. But, do you have a second pump in case your main pump goes out while you're away?
Salt systems have been around for quite a while and should not have to have a back up source of chlorine, just in case the salt system fails.
To answer your question, there is no problem with having a salt system and a tri-chlor feeder operating together. I would recommend, as was previously recommended, that the tab feeder and salt cell be plumbed parallel to one another.
Most systems have a Boost mode. Simply activate a boost mode before you leave so additional chlorine can be fed into the pool before you leave and should provide additional chlorine in the event that the salt system fails. The additional chlorine should keep algae at bay while you are away.