"The children are" is correct (third person plural).
HAVE or HAS is the simple present tense of the verb "to have" I have you have (singular) he, she or it has we have you have (plural) they have Examples are: I have a wife and two children. They have lots of money. Note "will have" is the future tense and "had" is the past tense.
The verb is is the present tense.
The past tense of did is did. The present tense of did is do. The future tense of did is will do.
It was, (past tense) it is, (present tense) it will be( future tense)
Past tense I had Present tense I have Future Tense I will have
"Has" is in present tense. The past tense is "had".
No 'is' is present tense. am/is/are = present tense was/were = past tense
Present tense
the present of did is didnt Do is the present tense of did. Didn't is the past negative form
Should is present tense.
Creep is present tense. The past tense is crept.
"Has" is the present tense form of the verb "have." The past tense form of "has" is "had."