Josephine I suppose that this is not really something you can easily discuss with a priest (I imagine that he would look quite surprised if you asked him "We want to give up sex for lent, when is the best time to give my husband a blowjob on weekends?", but if you both feel happy with your arrangement and see nothing spiritually wrong with it, why not?
Plus if it happens more than an hour after sundown, it is already Sunday under sabbath rules.