It's not that a 2nd rounder is unfair value in a keep 3, but I'd try to negotiate it down a little.
The thing about it is that most GMs will be looking to offload their non-keepers in exchange for something before the keeper deadline, so I think it's easier here for you to play the field a little and play other GMs off one another. Right now you're being asked to pay top dollar. Will someone else give the McLaurin owner a 2nd rounder? Doubtful, but maybe (and only then if there's another team truly lacking 3 other viable keeper options). Will anyone give him/her a 1st rounder? I'd be absolutely floored in that setup.
In other words, you have some leverage here that you ordinarily wouldn't in a midseason trade because you (and everyone else) generally knows who's selling what, and most of the GMs with "too many" keeper quality players would rather get something than nothing. So players that won't/can't be kept by their current owners tend to trade at a bit of a discount pre-keeper deadline.
Another strategy that I've used successfully in this type of situation is to offer the higher pick (here, for example, the 2nd rounder that's being asked) but say that you'd also need a lower pick coming back your way (for example, a 5th). In these situations in most leagues, acquiring another high round pick is viewed as the end all be all for the other GM--mainly because fantasy football is viewed as very top heavy (despite the number of really valuable mid-to-late round gems that emerge every year), but also because they can only roster so many players (so if they acquire an extra 2nd, their last round pick becomes moot). So all told, it's often fairly easy to convince the GM that the extra higher round draft pick they're acquiring (to bring in more marquee talent) is worth a mid-rounder in addition to a player they can't keep anyhow.
Good luck! Interested to hear what you end up doing.