for all wondering like me how in the heck do you convert a three wheeler like this.....this pic will help....it is one wheel in back and 2 in front
it is hard to tell but with OP's description and pic it looks like putting a claw hanger on will work
but is would help to understand more of OP's needs to give best suggestions... No coaster brake I get. Is there and issue with gearing ranges? how many gears is current setup
it is possible a wider range IGH may work also budget may make a difference