I don't think you'll have problems bumping the ground. Although I know you said you're not considering it, you may want to check out a set of clipless pedals for the heck of it. I have ridden most of my life on platforms -- only the past 5 years have been on clipless, and I still would be on platforms if I hadn't let someone talk me into trying them. There are good reasons why almost everyone goes this route
Normal looking cycling shoes that you can walk on wood floors exist. Especially on a trike, your feet are going to want to fall out when you stop at a light or sign. Power grips are probably the next best option.