You should not do the large water change until about 24 hours prior to the fish being added, as mentioned. The plants will be ok with the ammonia (but they will need proper light and nutrition, since the tank will not have any food for the plants yet.)
During the qualifying week, you should be able to dose the aquarium to 5ppm ammonia level and then watch it drop to zero ppm ammonia and zero ppm nitrite(NO2) within 12 hours of when the ammonia is dosed as measured by a good liquid kit. It should do this day after day, if it doesn't then it's better to start the week over (better to have it happen now than when it would be damaging gills and nerves.)
The final large gravel-clean-water-change should be "down to the gravel" with deep gravel cleaning (despite probably not seeing debris.) Its main purpose is to remove the large amount of nitrate(NO3) that will have built up during fishless cycling. If you have a delay in getting fish, it's fine to dose more ammonia as long as it's at least 12 hours or more before the fish come in for acclimation.
~~waterdrop~~