This is exactly what I do. It's a lot to ask a kid to do - no problems when things are fine, but a lot of things can happen at a boat ramp. Ramps are no places for kids - cars reversing with very little vision, the last thing people are looking out for is children.
The best advice is to have a routine - put things on/off in the same order - bungs, tie-downs, lights etc. Worst thing that can happen is that someone decides to 'help' you. That is when things get forgotten, get undone before they should etc.