That "both front and back yards flood during rain" is at least a major annoyance if not potentially a big problem. It needs to be addressed and solved before any planting takes place, as solving it likely would necessitate disturbing the ground surface, which would destroy plants. If the city is years behind in maintaining the ditch, it might never happen and you might want to do the basic ditch clean-out as part of your own repair to flooding problems (of course, with whatever approval is needed.) We couldn't tell based on the photographs what needs to happen in order to solve flooding problems. You'd need to get a landscape designer or someone with expertise to look at it locally.

In creating greater curb appeal, the first thing that jumps out as needing correction is the dead-end front walk. Its use has apparently been abandoned some time in the past. It either needs to be made useful and attractive ... or it needs to be removed in favor of improving the driveway route to the front door. I suspect that the driveway route seems adequate and that's probably the way I'd go. But it does need improvement. Limiting the walk to only below the overhang makes it too skinny and confined such that it could never seem welcoming. Consider adding on another path outside of the overhang.You could leave a couple of cutouts for planting at the columns. As the drive is not in great shape, you might consider replacing it as part of the process, widening it a couple of feet if possible.

A simple, basic landscape organization where the plants were in good condition would help the overall appearance. Given the shade and slope at the ditch, it might work out to have yard of groundcover, as opposed to turf. (The colors are not recommendations.)