I would think that they have a pretty decent cushion in that trade price, or they would not do it. That being said, we know they don't give much on trade, and they have extra cushion since they haven't seen it.
How much money are you leaving on the table by trading instead of selling?? $10k $15 ??
I'd at least try to sell it myself for a month or so to see what kind of interest you get. You will know in the first week if you will have much interest. If it doesn't sell, then you can always trade it. Might be well worth the hassle. Price it $5-10K over the trade in price and see what happens.
When we bought our TT dealer offered us $2000 for our Popup, I put and add on craigslist about 10pm on a Tuesday. My email and phone started blowing up. First person that called met me at the house after I got off work, and paid me $5000 (asking Price) in cash. I had 3 more people on the way to look at it, that I called and told them it was sold.