This all strikes me just as a matter of taste more than law, but nonetheless here's my two cents:
Many rabbis feel that having a celebratory meal on Thanksgiving has nothing to do with anything pagan and is permissible, or even obvious. (Rabbi Joseph Dov Soloveichik was noted as moving his lecture earlier on Thanksgiving morning so he could catch the plane back to Boston for Thanksgiving dinner at his sister's house.) Other than Shearith Israel of New York City, however, I don't think most Jews treat it as of particularly religious significance. (I did see one synagogue at the very liberal end of the spectrum skip Tachanun that day -- convenient as it's always long-Tachanun Thursday -- but that's quite a stretch.)
It is considered appropriate on Chanukah to have joyous meals, especially as that would enable you to recite al hinisim afterwards. So if you had family over, lit Hanukah candles (or even better, oil-and-wicks), then said "happy Thanksgiving", ate, and said the blessings afterwards commemorating Hanukah, okay fine everyone wins.
To whatever extent you felt like blending the holidays' "traditional" food items with a sense of humor -- pumpkin latkes or whatever -- well, fine. The traditions behind chanukah foods aren't all that strong anyhow, so it's not that big of a deal.
What bothers me most is the degree to which Chanukah has already been turned into yet another bland commercialized piece of Americana and lost its Jewish identity. This could make it worse.
"Hooray Hanukah, Pilgrims Maccabees whatever yay, now turn on the ball game, touchdown! Beer commercial! Minyan shminyan, stampede at Black Friday @5AM for hanukah presents!" Something's lost in the message there.
Rabbi Isaac Hutner, who had studied philosophy in Berlin, writes about Judaism's resilience in its tolerance to a great diversity of other ideas and cultures (this is called hod.) Extend a spring within its elastic limit, and it will return to its proper shape. (Thus in Hebrew we find hod ve-hadar, where hadar is Aramaic for "return.") Pull it too far, however, and it distorts and fails. Thus Daniel's vision of the Greek era talks about hodi nehpach alai lemashchit, "my openness to other wisdoms became destructive." Which is what happened when Jews got so much into "Greekness" that it came at the cost of Jewish observance.
While Hutner himself opposed observing Thanksgiving, I'd be inclined towards extrapolating from his Hannukah essay to conclude: can we celebrate both Hanukah as American Jews and Thanksgiving as Jewish Americans? Sure. But if we blur the line altogether, we're heading someplace dangerous.