Are you asking for 2018 or the upcoming 2019 tax return?
The new tax laws that went into effect for 2018 and onward eliminated personal exemptions, so you do not get an exemption for the kids or for yourself. Instead you get a higher standard deduction.
You say you are the custodial parent. Did you live apart from the other parent for at least six months of the tax year in question? If so, you should be filing as Head of Household--not married filing separately. If you can file as HOH then you are eligible for more credits including education credits and perhaps earned income credit (if your income falls within the parameters). What you were told previously about the $500 credit for other dependents for the 18 year old is correct, and so is the information regarding the child tax credit for the younger child. You can get the child tax credit until the tax year in which the child turns 17.
Am I Head of Household?
https://ttlc.intuit.com/questions/1894553-do-i-qualify-for-head-of-household
https://ttlc.intuit.com/questions/2900097-what-is-a-qualifying-person-for-head-of-household
If you qualify as Head of Household, when you enter your filing status (single or married filing separately) into Personal Info, and then enter your qualifying dependent, TurboTax will offer HOH as your filing status.
2018 Standard Deductions:
Single $12,000 (+ $1600 65 or older)
Married Filing Separately $12,000 (+ $1300 65 or older)
Married Filing Jointly $24,000 (+ $1300 each spouse 65 or older)
Head of Household $18,000 (+ $1600 65 or older)
Look at line 8 of your Form 1040 to see your standard or itemized deductions.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
