As an industrial hyginest and a shooter I've though 'bout this from time to time.
Granulated rubber berm material will prevent most of the problems associated with lead bullets striking armor plate. No fracturing or ricochets.
http://www.duelatron.com/granulated.shtml
Enough ventilation to move air from the shooting positon directly to an exhaust point you will also remove most of the contaminants generated there as well. Think of air returns overhead pulling air from right in front of you so that smoke moves directly toward the intake. A stack exhaust and blower that allows the exhaust to be blown upward positioned high up as possible on your house will prevent point contamination of the outside that could represent a hazard to children. If you prefer, you could use a P95 or HEPA filter system to trap the lead and other contaminant particles. Remember to wet or spray with something tacky (cheap spray paint, spray adhesive, or hairspray) that will lock the loose particles onto the filter, wear gloves when changing, and to seal in a garbage bag before throwing into the trash.
All surfaces should be sealed so that they can be wet wiped/mopped with a trisodium phosphate (TSP) detergent. Disposable wipping/mopping material should be used and tossed in a plastic garbage bag and into the garbage. Never sweep or vacuum (unless you want to pay for a lead abatement vac).
Carpet should not be used. Epoxy sealed concrete would be best. Rubber mats could be placed on the concrete for comfort. These should be washed down from time to time.
LeadCheck swabs (
http://www.leadcheck.com/LeadCheckSwab.shtml) are a color indicating lead suface contaminant indicator and should be used on a regular basis to verify that the anti-contamination systems are effective. Galson labs can send air sampling pumps and media for air sampling and this costs less than $100 for the materials and ananlysis.
Anticontamination step-off pads (
http://www.frhamsafety.com/nuclear/stepoff/pads.htm) should be placed at the exit so that contaminants are not tracked into the house.