Occasionally I am asked whether it’s all right for a Hellenic polytheist to worship the Titan deities. After all, doesn’t myth tell us that they were the enemies of the Olympian gods? Well, not necessarily.
At the very least, I think we can take it on a case-by-case basis. Kronos swallowed all his children (save Zeus), that’s certainly not a friendly act. And yet the Kronia was celebrated in Athens, by Athenians who worshipped Zeus as one of their regular pantheon. Besides, not all the Titans joined with Kronos to fight against the Olympians–Oceanos, for one, stayed out of the battle (he also stayed out of Kronos’ own struggle with their father Ouranos). And other Titans–Prometheus, say–have been helpful outright to humanity.
Even taken as a whole, the Titans are not evil beings. They are not chaotic beings. They harbor no desire to destroy the world–the Titanomachy, the battle between the Olympian and Titan gods for the rule of the earth, is in fact evidence of the value they place upon it. (I mention this because one reason often given in heathen circles for not honoring the Giants is that their intended endgame is the death and destruction of the Norse gods, during Ragnarok. Whether you find that line of argument persuasive anyway is beside the point–for the record, I don’t– because while there is sometimes a tension and an antagonism between Titan and Olympian deities in myth, there is not that sort of enmity.)
I don’t believe that there is any disloyalty in honoring the Titans in addition to the Olympians. I think that they are as willing to work with humanity as any other deity (which is to say, maybe they will and maybe they won’t :)). As always, I recommend doing one’s research first, but generally speaking I think it’s probably fine.