|So, if your child does not need or qualify for services or pull out from the classroom, then a 504 would be appropriate.
that is not entirely true, since many special education services are delivered IN the classroom setting. In our school (where I work) the vast majority of our children receiving special education services are served by learning support teachers who are IN the classroom during key academic periods and by modifications to the academic work within the classroom (i.e. materials at their own instructional level, different presentation of material, alternative testing methods, etc.) Of course, a subset of our students DO leave the classroom for services- primarily OT/PT/Speech with a very few having one-on-one or small-group time with the learning support teacher.
As for the issue of ADHD getting an IEP or a 504, it can qualify a child for either, depending on how it is manifesting in the academic setting. The VAST majority of students I diagnose with ADHD in the school setting (I'm a neuropsychologist and I work primarily in a regular-education charter school) either get NO 504 or IEP or get a 504. they get neither if their ADHD exists (i.e. I can diagnose it via testing/observation/rating scales) but they are not having significant difficulty in school (i.e. academic/social/behavioral/organizational). Of the ones that qualify for SOMETHING, most get a 504 under the category of "other health impaired". the twist is that each district is allowed to determine for themselves WHAT constitutes the level of "impairment" needed to qualify for a 504. In our school for example (and I had no part in writing these rules) a student with ADHD can have a 504 if they are getting below a grade of "C" in one of their major (like reading or math) subjects.
In general, an IEP is for disabilities that are directly related to learning (versus for example, a 504 could be for a child who is deaf and needs accomodations and modifications but actually does not have any learning disabilities). 90% of the kids I test who get IEPs have specific learning disabilites or speech/language impairments (I dont' diagnose these, I refer them). A few are autistic (or on the spectrum) and a few have what is called SED (serious emotional disturbance- though most of those get a 504 instead). a VERY few (like one a year) of kids with only ADHD get an IEP here, and that is when the condition is so severe that they are literally unable to learn (which is different than the kids who could learn more/better if they were attending or were more organized).
My advice would be to start with the 504 and to work with the school to be as specific as possible in the list of accomodations and modifications. This could certainly include a behaivoral component and a behavior plan to address issues related to ADHD (we often do this- to address things like attention, on-task behavior, social skills, decreasing disruptive or aggressive behavior, etc.) If that doesn't seem to be working the way you hoped, you can convene the "team" to adjust it. Unlike an IEP, it does not have to be re-done every year, but like an IEP, it CAN be changed any time, as needed.
If an adjusted 504 isn't "working", then you could revisit the idea of why an IEP is or isn't appropriate. There are certainly cases here in our school where we recognize that a child is not being served by a 504 (though we certainly expected it to help, and were acting in good faith) and re-evaluate to determine if the academic levels have changed (i.e. the child has not been able to learn as expected) and to see what the next step is in appropriate educational programming.
HOpe that helps...