Final decision of where to place these bodies will come in time, influenced by buy-in and eagerness of participating volunteers. The orbits of the planets are already calculated with the 18m Lake Eola fountain at the center, and that constrains the orbits. Here are the candidates.
You might be better off seeing these mapped. Orbits are elliptical, not circular, so we have a little flexibility about how far away from the Sun our planets are.
At this scale, the next nearest star, Proxima Centauri is 520 thousand kilometers away.
If you want to explore the math that goes into these calculations, you can try out the spreadsheet (Open Doc Format, great with Openoffice or Libreoffice).