Front mounted bike rack

A lot depends on the style of bike you intend to carry and the type of rack you use. Bikes with a tubular cross bar can be carried with a rack that clamps on the bar and will keep them lower out of the line of vision. You can also remove the seat. This does mean that the wheels are lower in front as well. If the bikes are a style that cannot use this type of rack, then you need a rack that will carry the bikes supporting them on the wheels. This raises the bikes more into the line of vision.
I carried some high-end mountain bikes once that required that they use a wheel supporting rack, and the vision impairment was such that I finally had to put them in the camper which was a big nuisance. Carrying them on the back wasn't an option.