You actually can do everything in the day time. You just need to gain a new habit when you wait or sleep. You don't even have to feed inside every 24 hours. What you need to do is pick a good time to be the 'feed time'. I use around 1am, which means when it's time to feed, most of the world is sleeping so you have a much wider range of buffet locations. If I need to rest, usually at level time, I'll travel to a mages guild, as the fighters guild has that stupid porter following you around everywhere. If you have a detect life ring/amulet/spell, use it, find someoen who is sleeping, and go into sneak mode and close the door to the room behind you. Then WAIT for 1 hour (waiting = select button). After you wait, you should get a message that essentially tells you that you've reached lvl2 vampire. The person in the room should still be there sleeping, make sure the door is closed and go into sneak mode. Then step up to the sleeping victim and feed. You'll revert back to lvl 1 vampire, and you can romp around in the sun all you like.

You don't HAVE to feed again inside of 24 hours unless you need to sleep or wait. Either of these activities after 24 hours will jump you to lvl 2. If you can keep the habit of saving your sleeps or waits until you're near a victim, and wait first, then feed, you'll be able to enjoy the benefits of lvl 1 vampirism without having to shy away from the sun. The best benefits are +5 to most of your stats, and resistance to disease. This is really helpful because you don't have to bother carrying cure disease potions, you don't have to worry about catching some gawd-awful abiltiy depriving condition and you have a small immunity to normal weapons. It's really rather useful once you get used to how to keep yourself at lvl1 vampire.

It is very important to note that when you do feed, you want to make sure you are in sneak mode, and have some kind of detect life spell or item going so that you can monitor the surrounding area, even outside your line of vision as you do not want to be detected feeding.