The games are only tangentially related, and should not be viewed as sequels to each other as much as they should be viewed as games that were cut from similar cloths. In terms of gameplay, in many ways the two are polar opposites of each other, but each are pretty easy to enjoy by their own merits.
I didn't have a frustrating time with the Last Guardian at all, but I treated Trico, and his inability to listen sometimes the same I treated my kid - with patience. And that's part of the point. All three of these Team Ico games feature gameplay elements that challenge video game expectations. Trico is supposed to ignore you on occasion and misinterpret what you ask of it. Go into it treating Trico like the quasi-wild animal he' represents rather than the AI you expect him to be, and you'll probably have a more enjoyable time.