What you describe brings to mind a very muted courtyard, which would be appropriate for the front.

I suggest you start with a study of the entire front yard space and develop first a size for the terrace that is in balance with the whole. The hardscape and associated elements should occupy a significant part of the overall space without over powering it. Where plants are used as part of the terrace complex, an element that separates the terrace area from the whole becomes more important.

Here is an old thread that MTO recently unearthed showing a front terrace, might give you some good thoughts.

The flip side of separation, of course, is access, so whatever you choose will have to do a bit of both. Also, a stone wall provides seating, while a boxwood hedge creates work. Which one suits you best in terms of your immediate capacity (budget/DIY) and long term maintenance?

Possibly if you post your approximate plan you will get more specific feedback.

KarinL

Here is a link that might be useful: Spazzycat thread