Drown by Ordis has a minor but vivid subplot/backstory with Loki as the parent of Fenris and company. The story is gen with Loki, Tony, and Steve, WIP: http://www.fanfiction.net/s/8116498/

Also, Trick Or Treat 'Til The Neighbors Are Gonna Die Of Fright by Kittenmommy is a short piece of enjoyable fluff with Loki as parent: http://archiveofourown.org/works/542049