1.She is driving to her grandparent's house.
2.I am reading a magazine.
3.They are playing with a board game together.
4.Tom is having lunch at a restaurant.
5.Our family is having a walk together.

Anny: 2. I am reading magazine.
Correct: 2. I am reading a magazine.
Explanation: A is an article that signals that the noun modified is indefinite, referring to any member of a group. Use a + singular noun beginning with a consonant.

Anny: 3. They are playing board game together.
Correct: 3. They are playing with a board game together.
Explanation: With is a preposition used to show method or a way of doing something.

Anny: 4. Tom is having lunch at restaurant. 
Correct: 4. Tom is having lunch at a restaurant.
Explanation: A is an article that signals that the noun modified is indefinite, referring to any member of a group. Use a + singular noun beginning with a consonant.

Anny: 5. Our family are having walk together.
Correct: 5. Our family is having a walk together.
Explanation: Is, the third-person singular present tense of the verb "to be". In this sentence, the word family is a set of parents and their children.