I think you’ll have less than 30% attend the chuppah & luncheon if you figure out the proper wording to invite everybody, or better yet have a family relative or even the Choson do the explaining. Basically have someone say “My ____ would love to have everybody over for the ceremony, but his house is just a bit too small. And the drive to CT is a big schlep. That’s why he suggests that only those that feel really close should come for the Chuppah”. Then leave it to each guest to determine his/her closeness.
If you can’t contact everyone verbally, maybe just put all the events in the invitation for everyone equally, but print something like “Intimate family & friends backyard Chuppah followed by homey luncheon at ______ @11:00.” You have the option of adding “Since space is limited please RSVP so we can accommodate all our guests comfortably” and mark the return cards accordingly.
If you get swamped by positive Chuppah responses and money seems to be no issue, rent a tent so your backyard can accommodate everyone despite possible inclement weather.
And btw every wedding also has Sheva Brochos, but the reverse is not true…