Jane...it may be easiest for YOU break up the collection into sub-sets.
I.E.: GM cars from the 50's, Italian cars, the perennial favorite....Ferrari, F-1, etc.Keep the subsets limited in quantity, perhaps only 25-30 models each.
That allows better focus for the buyer.Also decide if you are willing to sell one car at a time or some other grouping. YES, this will involve work for you, but ultimately should move the product.
Last but not least....do you have a list of the collection including model, scale, color and asking price(pictures would be very good ) to send out or post ? Can't buy it if I don't know you got.
Lotsa work but its probably the best way in the long run.