Sounds to me it would be better if it were tiered with landscaping block. If seeded, how will they keep the grass seed & soil from being washed away in a heavy rain storm? Who is responsible for keeping it looking nice? Will it be mowable?

Will there be a drop off from the sidewalk? What if someone falls? Who is responsible for possible injuries?

We also live in a small town of 3,500. Years ago, the city had land donated with a small pond. They made the area into a park...nice job. BUT, we too had a steep hill. They seeded it with crownvetch! Wonderful plant for holding the bank up, but AWFULLY invasive. It is a constant battle fighting it...keeping it out of our lawn and gardens, and maintaining the appearance. But of course, this was done before we obtained the property, so we have to live with it.

I think you need to re-visit with them more and ask lots of questions. Get them thinking about what is the best option for all involved.

Becky