Hi Lisa,
I agree with Brenda. My son just turned 2 last week (and I have a 3 1/2 month old daughter.) I had always thought that once my son turned 2, I would make him give up his paci. Two just seemed to be the magic age of when other people I knew (including my sisters) made their children give up their pacifiers. My son usually just used to use them for nap time and bedtime, and when he was around 18 months, I had weaned him of his nap time paci. If he was sick, or if there was something that was really disturbing him (like when we were on vacation and his entire routine was sort of blown away), I would let him have his paci more often.
When my son started sleeping in his toddler bed a month ago, I decided to let him have his nap time paci back. I knew I'd get sh*t from others for back-tracking, but it was the only way he would go to sleep for me. I really started to pay attention to the way his pacifier would really,truly "pacify" him. He could be this terrible, cranky, overtired monster, and I'd say "Do you want your paci?", and BOOM! Monster gone, sweet baby boy instead.
I started reading on-line about the importance (or non-importance) of making your child give up the pacifier. To my surprise, I found a bunch of articles / websites saying that "experts" no longer feel it is necessary to make your child give up the pacifier so young. I read more than one article that said that as long as your child gives up the pacifier before the age of 4, IF the pacifier had pushed the child's teeth out a bit, the teeth would move back into normal position within a month or two of giving up the pacifier. These experts also agreed that as long as your child didn't have the pacifier in his/her mouth all the time (and as long as it did not interfere with the child's ability to learn to speak), you should let your child continue to have the pacifier. They said it is important for your child to have some type of security object, so they can grow up feeling confident. Some children have blankies, some have a favorite stuffed animal, while others have their pacifiers.
Sooooo...with very good peace of mind, I have decided to let my son continue on with his pacifier use. (I talked to my husband about it, and I found out he agreed with this 100%, and that he never wanted me to make our son give up his pacifier at 2 years old the way I always did!)
I would recommend to try to encourage your daughter into using the pacifier only at nap time and bedtime...but do not force it. She is still so young, just 19 months, and the birth of your son is such a major change for her! My son is still adjusting to the birth of my daughter. On most days, he does great, but once in a while, he will suddenly resort to acts of jealousy. Just be patient. She will eventually grow out of it. I do try to tell my son that "paci's are for babies", and this seems to help him to get rid of it right when he wakes up, since he is "such a big boy now!" But like I said, I don't force it. I think that can only make things worse...
I wish you luck, and follow your instincts!!! I know you would like to listen to your pediatrician, but I feel that in matters that are not directly related to my child's health, I don't have to agree with our doctor. (For example, my son's doctor firmly believes in the cry-it-out system, and he told me to do this when my son was just 4 months old. I was completely against it...I did end up having to do it when my son was 15 months old and I was pregnant and decided I had no choice BUT to make him learn to fall asleep on his own, but that is a decision for a parent to make, not a doctor.) (I am teaching my 3 1/2 month old to fall asleep on her own by putting her down in her crib when she is almost asleep, and it is working! So I am hoping/praying I will NEVER have to make her cry-it-out!)
Good luck to you!! And congrats on your new son! (P.S. Good job on the breastfeeding; I breastfed my son for 6 months, but found that once my daughter was born, I could only handle breastfeeding her for 5 weeks!! It was soooo hard with my then-20-month-old running around...)