So we are thinking that this spring we would check out the GCV during DL F&W. any thoughts on the best time to go? We were thinking late May or early June but are not sure if that is to late for all the cool F&W events (ends 12 June?)
Weather-wise, early June *usually* is cooler and overcast part of the day, aka "June Gloom". Some people prefer that weather, others are surprised that California is not sunny every single day.

Late May is usually good, and our weather was 85 and sunny every day.
I stayed at the GCH (Villas were full, not surprisingly) 5 nights over Memorial Day weekend this year and did F&W. It was a bit of a last minute trip, so we didn't book any of the special events- those looked great! It was the last weekend of Food and Wine, so I would avoid that if the events are important to you. It's not like Epcot's F&W, at least not all the countries and carts, etc. It has lots of the smaller events, wine walks, cooking classes, celebrity chef events, tastings, etc that you do find at Epcot. That said, the F&W trip at GC was one of my very best Disney trips EVER! (And I have a lot of them- including 2 F&W at WDW.) I thought 5 nights might be a bit much... nope... we relaxed, enjoyed plenty of pool and DTD time, ate well, and took all the typical stress of rushing about away. I highly recommend it! I can't stress enough how wonderful it was to have our room literally right there in the park. Get wet? Run upstairs and change. Our family enjoyed the activities for guests, particularly the Power Walk through DCA before park opening! It was like getting a private tour FREE.

We liked it so much we did it twice. Plus, the Grand Cal is so gorgeous! It's my favorite DVC.
If you are wanting to book it- do it as soon as you can- because the new Little Mermaid dark ride is rumored to be opening around then! It's supposed to be spectacular and it will NOT have FP.