Can 'Terminator Salvation' be terminated by a 'Night at the Museum'?

Both 'Terminator Salvation' and 'Night at the Museum: Battle of the Smithsonian' opened this weekend being the top two contestants for first place at the box office on this Memorial Day weekend. 'Terminator' opened on Thursday giving it a head start over 'Night at the Museum'. It also comes with a PG-13 rating that will help bring in teens; as opposed to the previous three installments in this successful franchise which were of an R rated nature. 'Night at the Museum' is a family movie with a PG rating. Being a three day holiday weekend also means that families will be going to the movies together meaning kids will have an impact. The fact that it will also be playing on IMAX might give this movie an edge over 'Terminator' .

Which of these two movies will prevail and take the number one spot this Memorial Day weekend?
Which movie will families decide over (a futuristic sci-fi action movie or a fun for all the family kind of movie)?

If you have a prediction sound off in a comment.

UPDATE: At the end of the day yesterday (May 24) the box office had 'Night at the Museum' in first place with $53.3 mil and 'Terminator' in second place with $43.0 mil.

UPDATE 2: The three day holiday weekend box office numbers are in.
'Night at the Museum: Battle of the Smithsonian' $70.0 mil
'Terminator Salvation' $53.8 mil