The ex-pens are great, and even keep my two "big" yorkies in. We have one set up around a small ornamental pond in our backyard, it's out there in all kinds of weather, and its held up great.
We host "small dog club" in our yard one night a week in the summer, we stretch an ex-pen around the gate to our yard, and it acts like a second, saftey gate when people are coming/going with their furkids.
Also, we take one with us when we go places, indoors and out. It works well.
One point of caution.
DO get one with a door, and only put Gizmo in and take Gizmo out through the door. If he never goes "over the top" he may not see that as a means of escape.
It's worked for Bernie, my gate climber. He's never climbed out of an expen OR over our new wooden gate that hubby built for the foyer, and he's always gone in/out through the "door" of both of these.
Good luck! Gizmo should love his new "play yard"!