I think they’ll be kinda pissed! I have to imagine that after Amity kicked Willow out of the party when they were little kids, Willow went home and cried to her dads. I can almost see a scene where they’re trying to console their daughter while also exchanging looks over her shoulder expressing their anger over what Amity did. In my opinion, there was also a little bit of “I told you so” in their minds. The Blights parents were probably jerks to Willow’s dads growing up (perhaps they still are as adults), and they might have been worried when Willow befriended the Blights’ young daughter. They would have been sympathetic when Amity abandoned Willow, but I don’t think they would have been very surprised.
Amity and Willow reconciling, though? THAT will come as a surprise. Willow was clearly very upset about what Amity did. It’s clear up through Understanding Willow that Willow still dwells on it years later. And I get it - I’ve been through similar stuff, and it really does eat at you! I think that Willow’s dads will not only be surprised, but also nervous that Amity will hurt Willow again. We don’t know much about them yet, but I picture them as protective, and they’re very angry that someone hurt their daughter like that. In fact, I think they’ll have a harder time forgiving Amity than Willow will! They might be cold towards Amity, or ask Willow if she’s sure she can trust Amity, or just discuss their fears in private, but I think that Amity will have to work to gain their trust.
I would love to see this play in out in a season 2 episode. I’m not sure if it will or not, but either way I’m confident that we’ll get to see some more of Willow’s dads in the next season. Thanks for the ask!