Personally I wouldn't worry about it. A house built in 1970 should not have had termites. My house was built in 1939 and has never had termites (knock on wood...what was that crunching noise
), but if you want to make sure you have no -icide issues, you need to spread activated carbon on the soil. The best one there is is by NORIT. Unfortuately I have no idea where to get it. You can read about it at
www.norit.com. The carbon will 'adsorb' all the chemicals on your lawn in just a few seconds of exposure. It really is instantaneous. If you want another absorbant material in there, H-E-B sells a generic (Hill Country Farms) brand of kitty litter containing 100% Zeolite. You can spread that stuff out and there should be no chemicals getting through. Zeolite also is a great place for microbes to live.
After all that you can apply a thin layer of compost and the soil will be ready to go. I would not till anything to take advantage of the fungus and bacteria living in the soil currently.