One alternative to lifting the toddler and preschooler is to sit down and then have them come into your lap. Another, if you really MUST carry one of them, is to have them climb up into a chair, or even onto a table, and then come straight into your arms. This way, tho you are still carrying their weight, you are at least not lifting them from ground up--which is the hardest thing on your pelvic floor/womb right now.
The less you do, and especially the less lifting you do, in the first 4weeks, the faster your bleeding will stop and the faster you will return to pre pregnancy energy level. Giving birth is hard work, and it does impact your body--even if you feel great after birth, this is still true. I just talked to a 6days pp mom (not my client): she is very fit and had a great birth--she says she felt fantastic, right after and since the birth. However, she was still soaking several pads a day--when we discussed her life in the past week, turns out she'd already shampooed the carpets in her home, and a lot of other heavy work! But my pp ladies who take it REAL EASY for the first 2 weeks, usually are down to only a pad or 2 a day, within 3-4 days after birth, not even soaking them, and some are done bleeding within that 2 weeks entirely; most are barely spotting by then (at most). Less blood loss is definitely better for a mom in so many ways. Less lifting, and less work of any kind in general, is the way to let your womb close up and rejuvenate itself, along with the whole pelvic floor.