Adding a clause to a sentence in order to give more information about a noun is very common. Remember, doing this will not change the structure of the sentence. Make sure that the subject has a clear verb which agrees in number and person. If you get confused, you can simply take the extra information clause out of the sentence and it should make sense.
1. The mayor is on vacation.
2. The mayor, along with his wife and children, is on vacation.
In the first sentence we have a simple subject + verb + object structure. It is very easy to see that the singular subject “mayor" agrees with the singular verb “is" In the second sentence we have added some more information, a plural group: “wife and children" However, this will not change the simple sentence structure, or the verb. In fact, the sentences are identical: the second sentence only adds extra information.