On each character you want to automatically accept invites on type:
/autoaccept add NameOfInviter
You can repeat this process for any character you may want to accept invites from in the future. It'll also enable other types of "accepts" like trades, raid invites etc (by default). It's very useful! After all names have been added type:
/autoaccept save
Also consider using EQBCS commands to accomplish adding multiple characters faster and with less typing. For example:
/bcaa //autoaccept add NameOfInviter and
/bcaa //autoaccept save
MQ2AutoAccept