For gen peds, a community hospital is probably fine. For subspecialties, most community hospitals aren't going to have enough volume to really get a good experience in that specialty. And anything remotely complicated is likely being sent to the closest Children's hospital.
And Children's hospitals generally have plenty of cases to go around. I'm in a subspecialty at a large children's hospital with a residency and a fellowship, and we have at least 4 learners (including residents and medical students, not fellows) rotating with us at any given time, and most days, there are enough clinics happening that there isn't overlap in any of the learners (including fellows). Obviously, the more specialized, the more likely you'll run into multiple people wanting that opportunity, but I think our med students get just as much exposure to cases as our fellows, they just get it in a short time, whereas the fellows get it more longitudinally.
I also did residency in a children's hospital that didn't have many fellows, so our fourth year students were treated like interns on the team as inpatient services, and on outpatients, just worked around the residents--there was still generally plenty of cases to go around (at least on the regular services, not like ID or genetics).
