"We are still going to keep looking to see who becomes available, but Craig and Heidar are the last two which we added to the squad as a necessity rather than a luxury," Mackay told skysports.com.
"We have got a pretty small and very young squad here, so to bring both of them in was fantastic business.
"I'll still keep an eye out for recruits though, but they would need to add something to the group of players here."
Helguson made an immediate impast with two goals on Saturday.