These are my people! I've done a few layouts before, sans children.
Here's a couple with Hero Squad:
I've also combined them when neither kit was sufficient to do a single superhero. My Spiderman page has both. I've also done a Captain America page that I can't find right now that use both, plus BIM: Worlds America. It had the more muted reds and blues I needed. Flergs' Transfomers kit and the BIM Galactic Wars could also work well depending on the photos. Several movie themed kits with the reds, blues, and blacks would complement the two hero kits really well if you're focusing on the love of super hero movies.
And if you're looking for a way to keep it superhero-ish, but not cartoonish, then an Agents of Shield/Guardians of the Galaxy/Doctor Strange vibe could be amazing. I'd especially love any Doctor Strange elements (especially his necklace logo thing and his book) - he had a show back at Hollywood Studios a couple years ago that has been on my to-do list forever. Thor's hammer, Hawkeye's bow, Black Widow's little red logo, and Infinity stone gems would also be super welcome!