Selkie / Heartwarming

First off, pretty much any occurrence of "the happy-squeal" from one of the kids falls under this or Funny.
When Selkie first realizes that Todd isn't yanking her chain - he genuinely means to adopt her.
Selkie saying goodbye to her friend George.
Selkie: Tochte'kunet. Vahn sient toht... It's "Goodbye, my friends. I loves yous."
When Todd realizes how much Selkie has in common with his childhood self, and that he has an obligation to her.
Theo's parenting advice.
"Son, when an eight-year-old offers you their favorite food, don't recoil in horror."
"Sometimes, part of being a dad is knowing when to suck it up and eat the eyeballs."
Merigold quickly warms up to the girl.
Immediately followed by this.
Todd: Welcome to the family, Selkie.
The first day of Selkie's suspension (and throughout it, apparently), she gets to spend it with her grandparents. The Incredibly Lame Pun in the author's commentary caps it, though.
Andi is, justifiably, getting torn to shreds by Todd and his parents over having lied about Amanda being stillborn. Amanda comes to her defense in a combination of this and Tearjerker, as she's sporting some Berserker Tears by the end of it.
Amanda: YOU didn't take me back, Mom did! S-she hunted for me, a-and sleeps on the couch s-so I get the bed, a-and a LOT. You IGNORED me, and adopted THAT!
- It even triggers a (mild) Heel Realization in Todd.
  Amanda: ...the adults are apologizing? What witchcraft is this?

Heartwarming / Selkie