You can claim both the children since they are under the age of 24 and full time students under the Qualifying Child rules as long as they meet all the requirements.
If you claim a student as a dependent then any education expenses and credits are entered on your tax return. They should receive a Form 1098-T from the school and you report that form on your tax return. A student dependent cannot claim any education expenses or credits on their tax return.
The child can file their own tax return and report their income and taxes withheld. If their income is less than $12,200 they should receive all federal income taxes withheld back as a tax refund. Verify for sure that they are indicating on their tax returns that they can be claimed as a dependent or you will here back from the IRS.
To be a Qualifying Child -
1. The child must be your son, daughter, stepchild, foster child, brother, sister, half brother, half sister, stepbrother, stepsister, or a descendant of any of them.
2. The child must be (a) under age 19 at the end of the year, (b) under age 24 at the end of the year and a full-time student or (c) any age and permanently and totally disabled.
3. The child must have lived with you for more than half of the year. Temporary absences while away at college are considered living with you.
4. The child must not have provided more than half of his or her own support for the year.
5. If the child meets the rules to be a qualifying child of more than one person, you must be the person entitled to claim the child as a qualifying child.
6. The child must be a U.S. citizen or U.S., Canada or Mexico resident for some portion of the year.
7. The child must be younger than you unless disabled.
