I second Lisa K's thumbs up to Drs. Mike and Charles Slavik. Not sure if she mentioned but it's a father/son team so you get a ton of experience from Dr. Charles and cutting edge from Dr. Mike. Both are relaxed and easy going and we and our boys love them.
My youngest is small weight wise - but the way Dr. Mike handles it is that each kid is different and as long as they are showing consistent growth, then they're just growing at their own pace. If you kids went from a 50th percentile to a 5 percentile in weight without a substantial increase in height, then there would be cause for concern. But if you're kids have been consistently in the 5-10 percentile and continue to be, then it's just how they are - probably not a need for worry.
I know you're short on time and busy, but schedule an appt to talk with them before you bring the kids. We did this when I was pregnant with my first and it helped me feel comfortable and get their take on things without the distraction of a baby. And you don't pay for this type of visit.
They get us in whenever we need to, the front desk staff (at least at the rolling meadows office where we go) are really nice (recently picked up free formula samples when she saw me looking at the rebate forms on the desk) and they do have late hours. I can't say enough good about them.
(Plus, Dr. Mike has a philosophy that I love...if you find the poopy diaper, you change it. That includes him when he's checking out the newborns at the hospital as well as kids in his office!!)