Hi Emily!
I personally would not think Typhoon Lagoon's Gangplank Falls would be suitable for a 23-month old. The inner tubes are large, with not much to secure a small child, other than handles on the sides.
There is, however, Ketchakiddee Creek which is only open to those 4 feet tall or under (with adult supervision) which has slides, fountains, waterfalls, squirting whales and seals, a mini rapids ride and lots more. Castaway Creek is the 2,100 foot circular river which you can float around on, using the inner tubes provided. There is also lots of fun to be had alongside the surf pool -
again with adult supervision young children can enjoy the water's edge.
Blizzard Beach water park offers similar entertainment for young ones. Tike's Peak is a child-size version of Blizzard Beach (adult supervision is also required here). Cross Country Creek, is a 3,000 foot waterway which circles the entire park, and inner tubes are used to offer a relaxing way to float around this.
For more details on both water parks click here
Typhoon Lagoon or here
Blizzard Beach.
I hope you have a magical vacation!