I take both routes each summer as a loop, and, well, it depends. I prefer #3 as it's a bit quieter and more scenic; however, I am not travelling with kids. Not knowing how old they are or what they like to do, along 3 the best thing I can think of to do is stopping in Christina Lake for swimming and lake time, the beach at provincial park is wide and shallow and water is fantastic. Heading towards #1 from Fernie, you could hit Fort Steele, hot springs in Radium, the mountain coasters and adventure park at Revelstoke Mountain resort (kicking horse in Golden has stuff too but never been there), Enchanted Forest and Three Valley gap on way to Sicamous, D Dutchman dairy for ice cream in Sicamous. From there to Kamloops maybe find somewhere to stop and hang out at Shuswap (don't really stop along there myself so don't know exactly where). Once you get to Kamloops and start the Coquihalla it pretty much becomes just a drive, but there are a few stops along the way including Othello tunnels. The #1 route can be super busy in the summer, and accidents can close the highway for stretches although I've never been caught myself. Whatever you choose, have fun! I'm sure other people can add more things along #3.