Very good setup there. She can tease and flirt with him, and he can get relaxed at the same time. After dinner is done, she can take him upstairs for slow and steady sex, since the edge has been taken care of.
Or fuck right on the floor, so the slave can see, hear, and smell the sex, but they are not touching her. Once every few days, the wife might use her fingers to force her to orgasm for half an hour, as a reward. The rest of the time she keeps the toy in lust, and thirsty.