You are getting advice on two different things: a baby carrier for babywearing and a baby backpack. I used a baby carrier, a new Snugli with the waist belt, until my daughter was about 6-8 months, and then switched to the backpack. I am short, 5'2", and have big boobs, like 36G, so having more weight on my back was a HUGE difference for me. Carrying her in front was really hard on my back. Your younger one will grow out of the baby carrier before the backpack, and at 24 pounds I would say the backpack is a better choice. Some of the baby carriers can carry on the back, like the Ergo, but I think at 19 months and 24 pounds the backpack will be easier on your body. My daughter is now over 2 and still loves to ride in the backpack. We have a Deuter Kid Comfort II, and I would thoroughly second the recommendation. Both my husband and I can wear it comfortably, it carries lunch and a few diapers easily in the under seat pocket, and it is very easily adjustable for kid size. She's been in it since she was about 6 months old and she's always loved it. And my back has loved it too. She likes being up high and looking around, and it's good up to 50 pounds, which the baby carriers aren't. I don't think she'll be on our backs anymore when she weighs that much though. I love our Deuter, and I would recommend buying the sun shade for it if you get that one. In Florida, it's essential. I would also recommend going to REI and trying some on so you can find the one that fits you and your son best too.