My wife is usually too tired to have marital relations at night. She prefers the morning, after sending the kids off to school, when she feels more refreshed and uninhibited. Is this OK?
Nothing will wake her up
A husband is permitted to engage in marital relations during the day if his wife shows her desire for it, or if he feels that he will otherwise think about other women and thus fall into sinful fantasies or actions. However, because it is generally forbidden to have marital relations by day, or in a lighted room, we will quote the laws as summarized by Rabbi Mordechai Eliahu, former Chief Rabbi of Israel, in his book, "Darkei Taharah," Chapter 22:
It is stated in the Talmud, "Rav Huna said, ‘The Israelites are holy and do not have marital relations during the day.' Rabbah said, ‘If the house is darkened, it is permitted'" (Niddah 17a). If he is a Torah scholar, and thus careful to cover himself with a blanket, it is permitted. But this permission is only to be allowed in extreme circumstances, as when he sees that his desire is overcoming him, or he sees that his wife is acting seductively to attract his attention, as the Talmud describes (Ketubot 65a). When marital relations are conducted during the day, it must be in a darkened house, or under a covering that covers all of them including their heads for the sake of modesty, which we will now explain in detail.
A person should not engage in marital relations where there is light because of modesty, whether it be daylight, moonlight, candlelight, or electricity, etc. Someone who has relations by candlelight may cause his offspring to be epileptic, even if the wife is already pregnant. In the cases that we mentioned when it is permitted to have relations in the daytime, it must be in a darkened house with the windows shut, and other similar measures, even though the darkness may not be total. A Torah scholar who is modest in his ways, and who will not look at his wife's nakedness, can have relations where there is daylight when he covers himself and his wife with a covering, but this should only be allowed in cases of great need. Likewise, with all other men, if they feel that they will otherwise come to transgress, and the house is not darkened, they can cover themselves like a Torah scholar, but they must be very careful to act modestly like a Torah scholar acts.
Turning on lights in prohibited
The covering must be extended over their heads and beyond their feet, so that absolutely no part of them can be seen, and the covering must be opaque, that is, not pervious to light.
It is forbidden to have relations by candlelight, electric light, and the like, even if the light is darkened by a covering. If the candlelight is in another room which lights up the room where they are, a Torah scholar can cover themselves with a covering and engage in marital relations. If the candle or light are in the same room, he can set up a curtain (mechitzah) that divides the room into two, making it like two rooms, and thus a Torah scholar can cover themselves with a covering and conduct relations. The length of this room divider must be 192 centimeters with a height of at least 80 centimeters. It must be sturdy so that it will not sway if there is wind. On the Sabbath day, one should not set up a divider like this, unless there are special requirements that can be met.
There is another possibility if he cannot extinguish the light, and that is to cover it with a vessel or thick towel, or the like, even if a weak dim light remains, and this may even be done freely on the Sabbath and Festival Days, but on these days, he must be careful not to extinguish the light in so doing.
If it is impossible to cover the lamplight or candle in any manner, there are Torah authorities that permit a Torah scholar to have relations by covering himself and his wife properly, and this permission is extended to others as well, if they are not having relations to bring about a pregnancy and if the wife is not pregnant (whereby relations in a lighted room could harm the offspring).
There are Torah authorities who permit a newly married couple to engage in relations in the presence of light on their wedding night if the bride is a virgin, because the wife usually does not become pregnant through this coupling, thus there is no danger to potential offspring, as has been mentioned. This permission also applies to the devoutly religious on their wedding night. However, if the man fears that seeing parts of his wife's body will repulse him, then this permission is not extended. But if this first intercourse is difficult for him, and the darkness makes it all the more so, he should consult a qualified rabbi.
An alternative solution is that your wife take a nap in the afternoon or early evening, or in the morning after sending the kids off to school. That way, you could most properly conduct marital relations at the most propitious time, after midnight, when the kids are fast asleep and your wife is more refreshed because of her nap.