Here's good news: the description of "Werebears" (MM page 207) describes how werebears usually only infect their chosen companions or apprentices with werebear lycanthropy (and then spend time with them to help them control it). So there's precedent in the Monster Manual for characters choosing to accept the "curse" of lycanthropy as a gift.
Here's bad news: the "player characters as lycanthropes" sidebar (also MM page 207) says:
lf the character embraces the curse, his or her alignment becomes the one defined for the lycanthrope. The DM is free to decide that a change in alignment places the character under DM control until the curse of lycanthropy is removed.
All the sources I can find tell me that kenku are strongly chaotic creatures; wereravens are lawful good. This is a major alignment shift! Kenku might view this as akin to mind-control: yes, it's power, and that's great, but after you do this you wouldn't be you any more.
If a kenku embraced the change and became lawful good, it would be difficult for them to fit in to kenku society. Most kenku are mischievous tricksters and many are criminals, and a lawful good creature might not enjoy interacting with such creatures.
Here's how your DM should feel about a PC doing this: your DM should be very uncomfortable with a character embracing lycanthropy, simply because it's so powerful. Very few of the creatures your group fights will have magical or silvered weapons, so the lycanthrope will be essentially immune to those encounters. Flying also makes you immune to a broad class of encounters (ie, encounters with creatures who can't hit you while you're flying). If you do this, it becomes much more difficult for the DM to design an interesting encounter.
Of course each DM is different. Some DMs might be okay with having this happen, especially if it happens to the whole group at once; other DMs might follow the rules text above and convert the kenku PC into an NPC.
Think about worldbuilding: Leaving aside the question of kenku for a moment, there's an opportunity for worldbuilding here. If being a wereraven is really so great, why doesn't everybody do it?
Maybe everyone does do it, and your group periodically encounters villages that are 90% wereraven/werebear/weretiger/etc.
If not everybody does it, the DM should think about why that is. Maybe the wereraven alignment change is more than just being lawful good; maybe wereravens are fundamentally different (obsessed with shiny objects, opposed to hats) in a way that makes most villagers reluctant to embrace lycanthropy. Maybe villagers are superstitious and biased against wereravens. Maybe there's something else.
But remember: kenku can't read the Monster Manual. In practice, an NPC kenku considering this isn't going to say: "well, the weapon immunity is good, but the alignment change isn't compatible with my rogue skills..." Instead, the conversation will go: "Hey, if you let me bite you and infect you with this disease I'm carrying, you'll grow wings and be immune to weapons! Trust me, this will be great!" Kenku can't really know for sure what downside there might be for accepting this offer, and it's all going to come down to trust.
(And, note: the wereravens you're talking about are from Curse of Strahd, ie, Ravenloft. Ravenloft is absolutely dripping with things that will lure you in with offers of power and then turn you evil. A very learned PC might be able to identify that this particular offer of power doesn't come with crippling drawbacks -- but most PCs that are willing to accept this sort of bargain probably won't last long in the Ravenloft setting.)