I have to agree that Ebay is definitely not the place to sell these.
I don’t know why but many good quality collectables don’t seem to acheive good prices on Ebay and conversely some buyers seem to pay a lot of money for poorer quality items.
The big auction houses who are likely to get you a good price tend to charge a fortune in fees and commission.
I can put you in touch with an aviation art dealer who is also an aviation artist who may be prepared to sell them on commission but I am not sure that he will have the funds to buy them. If you are interested please send a PM.