Both resorts are good and I've heard good things about snow tubing at both. Horseshoe is the bigger of the two and offers a lot more than just skiing and snowtubing, ie snowshoeing, cross country skiing, so it tends to be very busy. Snow Valley is closer to the city so it would require less driving to and from the resort from the hotel.
Just to let you know, the Super 8 is on the south end of the city and both resorts are north. There are a few short cuts/side streets to take to each resort, but the 400 highway goes right through the city, so it's easy to get around.
There are a lot of great "non-chain" restaurants (and stores) down town, but if you're going with kids you may not want to go to those. There is an Eastside Marios right beside the Super 8. Nearby there is also a Jack Astors, Boston Pizza, Kelsey's, Montana's and a Casey's in the Barrie Molson Centre (where the Barrie Colts play). There is also Retro Planet just across the street from the hotel which serves pizza and burgers but has an arcade similar to a Dave and Busters but for younger audiences (I'm not sure how old your kids are). The Market Buffet is okay but I haven't heard too many good things about it since it opened. There is also a Cora's in the area if you were thinking about places to eat for breakfast.