help me

ok, any moms with more than one kid, I need some advice. What to do with the older one while putting the baby down for a nap? One solution is to put the baby down awake, but I'm pretty sure I missed the boat on that one and we usually nurse until he falls asleep. After that, he's really very easy to lay down in his crib. The trouble is that Laura really wants to be around us. She tries to be quiet, but she's 3! I've tried getting her set up with TV, a book, a snack, playdough, etc. but she inevitably ends up crying for me to come back or coming up to find us while I'm nursing him.  I end up mad at her and yelling, she cries more, and he wakes up, never to sleep again. He will fall asleep in a carrier on me, but I can't do that all the time and he won't sleep for nearly as long as in his crib. The other day, Jim took Laura on an adventure and Adam slept for 4 hours in his crib, so I know he can do it and wants to do it. But what to do with Laura? Should I just relax and let him sleep when or where he gets it? Or set some serious ground rules for her while I'm putting him down? I feel like I'm constantly worried about his sleep. This is definitely our biggest source of stress during the day. Any advice would be great.