Transformers 3: Dark of the Moon...?

For those that have seen the movie:

I have two younger sisters who absolutely love the Transformers
movies. I would like to take them to see this next installment,
however, I am concerned about certain scenes.

I noticed in one of the trailers that Sam and the new girl were in bed
together and I want to know how inappropriate the scene was. I do not
think they are old enough to be watching sex scenes or dirty scenes.

So, does the movie have scenes where I would have to leave the theatre
for a few minutes or is it just a two second type scene that leaves it
up to the imagination where covering their eyes would be sufficient?

If the movie has inappropriate scenes I will see the movie myself and
then wait to rent it for them so I can fast forward the scenes.

Thank you!