I worked in Special Ed as a teacher & Behavior Specialist for 12 years & a few things about your post either don't make sense or concern me... possibly because you didn't mention what "they" thought was wrong with your child. Does he have ADHD or is he on the Autism Spectrum, or??
The sentence, "Problem is all this has come out of the blue in the past few days and we have to make a quick decision if do want to take the In-Home Daycare place" makes me think either you are only comfortable sharing part of the story-or?? because there are major pieces missing... Schools generally do not want to pay for evals, so there must have been "something" to initiate the testing.
I agree that some children learn negative behaviors in a setting with other disabled children, however, I also believe some children make huge strides in a very structured setting. A 4 year old is not supposed to be able to make important life decisions & needs structure.
I have worked with parents that don't want their children in appropriate setting (or medicated) when it was in the best interest of the child AND I have also seen a teacher zero in on one child & make life harder than it has to be... so if this is truly a one time thing (that you don't see at home, with friends, at church, in the park, on playdates, etc)- then go w/ you gut.
If you really mean that this came out of the blue, then try the school you wanted, just have a back-up in case he is thrown out. Also, make sure they are offfering you whatever services he needs/deserves (PT/OT/Speech/counseling).