If you're not doing a lot of closeups, there's no reason to use high-res figures like DAZ's. Posette, the P4 woman, would probably be fine for long shots/landscape scenes.

Register at DAZ3d.com. If you register and don't buy anything, eventually they will offer you free lo-res versions of Mike and Vicky. They can use the same clothing and textures as the regular Mike and Vicky. Also wait for them to offer a free month in the Platinum Club. They've been doing that a couple of times a year. That way, you can get the Turbo Import plugin that lets you put Poser figures into Bryce for just $1.99.

Eventually, you may decide you want to buy the newer DAZ figures such as V3, but there's no need to rush into it.