Hi Ellen, I too panic on and off in the last trimester (and at other times too

), I had a 19m gap and then a 17m gap between my girls. Part of the 'easyness' depends on the personality of the toddler but for the most part I find the gap works well. Need to change a nappy? Change the other while you're at it. Then the other things I learnt were to do sitting down times together (so I could rest but still give the older one attention) such as nail polish, hair brushing, shape sorting (Maddie is probably a bit young for that but she might enjoy trying), colouring, etc. If you don't already, put some of Maddie's toys away so that you can circulate half and half every few weeks to keep her interest up.
The best thing is that Maddie is probably still day-sleeping so you will regularly get moments where one or the other is sleeping and you can spend one-on-one time, or even when they both go to sleep at the same time! And when Kalem is home from school he'll probably enjoy playing with either of the girls and even help out with spoon/bottle feeding when that time comes.