I didn't think they had more than a few members
They're gaining followers. Hate attracts some people. They protested a funeral in Yakima. If permits are required, you can bet they have theirs, and it will be as close to the church as possible.
I seriously doubt that. From what I've heard, this alleged "church" has only 22 adult members, including Phelps, 9 of his 13 grown children and their spouses, and maybe a grown grandkid or two. (There may even be 2 or 3 members of this "church" who aren't part of the Phelps family. I don't know). I think they usually only send about a half dozen or so of their professional provocateurs to any one event, so they can cover multiple events in one day.
Four of his 13 kids are estranged from the family and tell lurid tales of incredible abuse at the hands of their father when they were growing up. The other 9 are all lawyers (or disbarred lawyers like their thrice-disbarred father). For years they have made a very lucrative living by provoking individuals and government authorities to go after them, and then turning around and suing those people and collecting big out-of-court settlements. Check out Fred Phelps on Wikipedia.
Hate attracts some people.
Well now, the words of millions of Bushophobes infesting our Blue states certainly back you up here! (But the Phelps family is certainly not attracting any followers with their message of hate).