I'm sure the site is legitimate, but it's accurate to observe that this article in particular is based on an online poll with self-selecting participants. It's just not a great way of doing a poll. That doesn't mean that broad observations can't be made from it, e.g. that some physicians are vaccine-hesitant with regard to this vaccine and 5-11 year olds, but the methodology is completely inadequate to say what proportion that actually is with any confidence at all.