We're just back from a trip to Alton Towers with a teenager and 5 year old. We stayed at the AT hotel for two nights, with tickets for the waterpark and AT. Early ride time included with the tickets is brill (and absolutely necessary IMHO!). We headed straight for CBeebies Land and were able to walk straight onto all the rides from 9am - 10am (we went Tues and Weds, not in English school hols). Queues seemed to build up quickly after 10am, I can't imagine that it's much fun waiting for longer than about 15 mins with little ones.
I thought CBeebies Land was excellent - very well done, and the Big Show Time arena was great, with Mike The Knight, ZingZillas, Nina and the Neurons. Plenty of spotlessly clean toilets and a good food place (not cheap!).
After CBeebies we went to Mutiny Bay for a couple of rides (no queues), then hopped onto the Skyride to Cloud Cuckoo Land for Charlie and the Chocolate Factory, IceAge 4D, carousel, frog hopper, Wobble World and the driving school, and didn't have to queue for any of those either. Queues started to build up after 1pm for the Charlie and the Chocolate Factory ride. Then we did the Runaway Mine Train with a short 10 min queue and another short queue for the River Rapids and Flume.
There's a funny pirate show during the day (you can watch it over lunch in the courtyard) and entertainment in the evenings at the hotels.
You can download the Alton Towers app to your phone so you can check queue times for the rides when you're in the park, and it also has offers for food and discounts in the shops. If you're going with another adult and want to do the big rides, ask for a parent pass at Guest Services; one of you queues for the ride, gets it stamped, gives it to the other, who can then enter the Fastrack. I'd also recommend the single rider queue - when the queue for The Smiler was over 90 mins, teenager and I went single rider and were on almost straightaway.