I assume not. McLaggen would've graduatated, since he was a 7th year in "-The Half-Blood Prince". And McLaggen is not in Dumbledores Army. Ron Weasley would sooner shave his head than let "McLaggen" join the D.A.
No mention is ever made of McLaggen being a member of the D.A. therefore we might assume he was not a member. McLaggen was, however, a Gryffendor so I do not think he would have been "too scared" to participate in the Battle of Hogwarts. Rather, I think McLaggen would have already left Hogwarts and was never informed of the Battle of Hogwarts in order to attend and help defend the school.
While it was never mentioned that McLaggen returned to fight, Oliver Wood and others, especially from Gryffindor, returned. The Deathly Hallows Part 2 gave a nod to this when Wood and several other flew in on their broomsticks. The only way you know that it is Wood is if you activate subtitles on the DVD. Oliver is the one calling to the others to come on.