Setting a schedule is the hardest to do since you are changing numerous things throughout the day as well as numerous people. Certain patterns of living has been established and now you want to change it. It is possible but be prepared for set backs. Realize that it doesn't mean it can't be done and keep doing it.
I would start with one item of the day you really need to change. Trying to tackle the whole day will be overwhelming for both you and the other people in your life. So pick either the time that you eat or the time you go to bed whichever really works for you.
Now here are some hints for each individual task you might tackle.
Form a bedtime routine. Make a chart and hang it up. For your three year old make it pictures. Things like a picture of pjs, then a picture of brushing teeth, then a book, then a bed. Whatever you want your routine before bed to be. If you want them in bed at 8 then start the routine early enough for to get thru each item and then lights out. Have your little one look at he chart and then you go do the item, come back to the chart and then go do it and so on. When you reach the bed one, tell them that now everything they needed has been done and now it is time to sleep. Tuck them in and kiss them and then leave the room. When they come out (notice I said when not if) Gently remind them that the chart says bedtime and place them back in bed. Don't let them getting out of bed get to you. Just constantly and consistently place them back in bed. After three times out of bed don't say anything to them just put them in the bed and leave the room. Promise yourself that you will try this for at least a week (7 full days.) You will see change in that time. Be also prepared for added behaviors like tantrums, hitting, acting out. Just stay with putting them back in bed and stay calm yourself.
Now for you. Realize that if you put them to bed earlier they will get up earlier, so you have to get yourself on a new schedule too. You need to go to bed earlier so you aren't cutting down your sleep time too.
Set a time for meals, make it and then give it 30 minutes to sit there. If your child does not eat don't worry. At the next meal time present food again and she will eat. The trick is to not give in in between the meals. Even if she acts like it is killing her. Once you get that establish then she will be fine. I would also recommend setting a meal or snack every three to three and a half hours. Breakfast at 8 lunch at 11:30, snack at 2:30-3:00 and then dinner at 6. Kids eat better on this type of schedule. Also plan not only your meals but your snacks too. You are more likely to do it if it is planned. Again write it down. Post it on your fridge or on the cabinet door. Stick to your schedule even when out and about. If you eat lunch at 11:30 either pack a lunch to eat at 11:30 or eat at a restaurant at that time.
Sorry this is a book. I will answer any questions that you have. You will definitely find that it will be so much easier when you get this going.