Hi M,
At five months old, my son took usually three naps a day, anywhere from a half hour to two hours at a time, and I would just watch him for tired signs and then do one of the things that always helped him go to sleep: take him for a drive, a ride in the stroller, or a walk in the sling or wrap. Feeding was on demand but he usually ate just after and just before a sleep. He'd go to sleep for the night anywhere between 8 and 10 at night, cluster feeding until he was deeply asleep. Basically, we were pretty unpredictable with time, although we followed a fairly predictable pattern. I finally decided that my son was ready for a bit more of a schedule at 11 months. By that time he was napping twice a day. I picked 9am and 2pm as good times since they were convenient for me and common nap times for him, and instead of waiting for him to show tired signs, I'd just go ahead and nurse and then do the sleep-inducing thing. It worked a treat and he was very happy with it. I also started putting him to bed at 7pm, with a dinner-bath-breast-book-brush routine and then a walk in the sling. He slept to between 6 and 7 am just the same as he had been doing with a later bedtime. He started complaining at being put in the sling or stroller at nap time and taking longer to fall asleep, and shorter naps, about a week ago, and so I just put him onto a 1-nap "schedule" and he's happy again. I nurse on demand as well as trying to get solids into him whenever he seems interested, but again, the nursing falls into fairly predictable time slots around sleeping: just after breakfast, just before and after (or in the middle of) his nap, and after his bath before bed are the rule, with extras when he feels like it. Mine, too, seems to sleep longer when I'm sleeping next to him, and that is also how I usually manage to keep him in bed longer in the mornings! I quite like the excuse to have a siesta! Perhaps even your 3-year-old would be happy to come and lie alongside you and have a quiet cuddle at afternoon nap time? I hope that this info is of some use to you!