Yes you can rent Surrey bikes on the boardwalk at the Boardwalk Resort, they are avaliable from 10am to 10pm. The cost varies on the size of bike you need:
2 seater is $18 (plus tax) for half an hour
4seater is $20 (plus tax) fo half an hour
6 seater and Grand (can fit up to 9 w/5 peadling) are avaliable but you have to check with the location for pricing.
You can also find Surrey bikes at:
The Caribbean Beach, Coronado Springs, Old Key West, The Polynesian, Port Orleans, and The Wilderness Lodge:
2 seater $16.90 (plus tax) for half an hour, and 4 seater $20.65 (plus tax) for half an hour)