My 5 month old has a nap every 1.5-2h and it makes planning any activities, e.g. swimming, v.tricky. The longest possible stretch she will stay awake is 2.5h and only if I keep her entertained the entire time otherwise she will be super-ratty. She, therefore, sleeps at 8.30ish, 11ish, 3ish and 4.30ish and bed at 7pm. Her 11am nap can last between 1-2h. The timings of her naps depends on what time she wakes up in the morning but her bedtime (by her own choosing!) is always between 6.30-7.30pm. I have no idea how to coordinate two little 'uns!