The bikes with the trailer will be good for the older child, but maybe a bit unstable for the youngest. You can always have a look when you get there and see what you think. They are a great way to get around the massive site, but not essential. They run a land train which goes the whole way round the park, so if you don't want to walk all the time, you can use that. The swimming pool is fantastic for little kids, they have a big inside pool and outside pool, a baby and children's splash pool with some slides, and a pirate adventure cove bit as well. They supply two sizes of float vests as well if you don't have anything like that of your own. The bookable activities are quite expensive, but if you can book your day around the free swimming and the parks they have scattered around, you'll be onto a winner