Given that there tends to be plans within plans, I could see either the information or the child being the ultimate goal with either being the front for the other. Also, Lara Raith is a member of the venatori which ultimately works for the Archive, so she may have received a directive to rescue the child and then made a plan to do just that.
The Fomor definitely believed the child significant in some way to have captured her. They then sent a high ranking official to retrieve both the plans and the child with us uncertain as to which was more of a priority for them. (It has been awhile since I've read it, perhaps they did state their apparent priority.)