first you need to know your audience as much as possible.
young, old, browsers used and whether they are people to use keys or mouses.
I think you understand all that so you need to cater for all eventualities. problem is it will take foreva to accomplish your task so pick one and get it online and enhance later with the other if need be.
as for browsers: they are close to standard now so that is less of a problem to what is was a few years back. Unless your audience uses mobile devices, then you will have a headache. nothing is impossible just takes longer.