Honestly I think you should hold off. Ridley will need time to be what he was last year bc the Pats offense just isn't as strong. He also has a pretty tough schedule ROS so it's tough to say he's going to bounce back nicely. Edelman is ok and will have some really good weeks but he's just not an elite receiving option, and would be a low end WR#2 at best. T. Smith is the intriguing option because he's a bit of a buy low, but he'll always be boom or bust, and you already have Shorts who is much in the same mold.
The only reason I would consider this trade is if you feel like DJax won't be able to hold his ground as a #1 WR. Right now this trade looks like you trading away a WR#1 and RB#4 for an RB#2 (Ridley) and two low end WR#2's in Edelman and T. Smith.
Personally, I would try to sell Starks to the Lacy owner (or buy low on Lacy) and stick with your current receiving corps. You could also might be able to package Bryce Brown to the McCoy owner for a decent return. Because your league has no flex option and starts 3 WRs, owning DJax is better than owning two lesser receivers, and MJD vs Ridley is a negligible difference.
Yahoo 12 team Keep 7 League (keepers in bold)
Cats: G, A, PPP, SHP, +/-, PIM, SOG, Hits, W, GAA, SV%, SHO
Start 10F, 4D, 1 Util, 2G, 4 Bench
F: Malkin , Neal, Parise, Benn, MacKinnon, Pavelski, van Riemsdyk, Tarasenko, Yakupov, Hanzal, Scheifele, Palat, Zuccarello,
D: Giordano, Seabrook, Gudas, Gologoski, Ehrhoff, Bieksa (IR)
G: Rask, Lehtonen, Mason