Kermit,
As the "other" women i dont think it is wrong to meet the new partner at all. If the new partner does not have kids of her own, remember she is new to this all, being a partner to a dad who has kids is one thing, but to be a partner to a dad who has autism is hard work. Have you thought about communicating to the new partner through email or written letter as to what you would wish to do, it would be less intimidating and would give her the chance to make up her mind as to whether she wishes to work as a group or leave it to yourself and your ex partner. As this situation may be frastruating for you, allow your ex and his new partner to figure out their relationship before questions get thrown at her such as is she ready for this. By allowing them time you are more likely going to have their cooperation.
Best of Luck!