MLK is a regular business day for us. (yay) Can we count this day for LE & CDs, and even fund on this day if we have a closing?

You can close a loan and fund it on a holiday (unless state law disallows it). But MLK day is not counted as a business day for rescission and other events involving the counting of precise-definition business days. Examples: the three-day period for presumption of not-in-person delivery; the four days before consummation requirement for revised loan estimates; the receipt of the closing disclosure at least 3 biz days before consummation.

... even if your bank is fully open and operational on MLK day.

The 3-day rescission period uses the specific definition for business days. That definition does not vary based on whether the lender is open for business on any given day. MLK is NOT a business day for rescission purposes, regardless of whether the lender is open for business.

A “business day” for purposes of the TILA rescission period means all calendar days except Sundays and the legal public holidays specified in 5 U.S.C. 6103(a). MLK is one of those legal public holidays. [See references below]

But I see no problem funding on that day provided that the required 3 business days have elapsed prior to that date. For example, if the loan closes and the borrower has received all required disclosures no later than January 11 then funding could take place on or after Sunday January 15.

TILA, Regulation Z, 12 CFR 1026.2(a)(6)
Business day means a day on which the creditor’s offices are open to the public for carrying on substantially all of its business functions. However, for purposes of rescission under §§1026.15 and 1026.23, and for purposes of §§1026.19(a)(1)(ii), 1026.19(a)(2), 1026.19(e)(1)(iii)(B), 1026.19(e)(1)(iv), 1026.19(e)(2)(i)(A), 1026.19(e)(4)(ii), 1026.19(f)(1)(ii), 1026.19(f)(1)(iii), 1026.20(e)(5), 1026.31, and 1026.46(d)(4), the term means all calendar days except Sundays and the legal public holidays specified in 5 U.S.C. 6103(a), such as New Year’s Day, the Birthday of Martin Luther King, Jr., Washington’s Birthday, Memorial Day, Independence Day, Labor Day, Columbus Day, Veterans Day, Thanksgiving Day, and Christmas Day.

5 USC 6103(a)
Holidays
The following are legal public holidays:
New Year's Day, January 1.
Birthday of Martin Luther King, Jr., the third Monday in January.
Washington's Birthday, the third Monday in February.
Memorial Day, the last Monday in May.
Independence Day, July 4.
Labor Day, the first Monday in September.
Columbus Day, the second Monday in October.
Veterans Day, November 11.
Thanksgiving Day, the fourth Thursday in November.
Christmas Day, December 25.

Thank you this was just the information I was looking for!!

Just remember to calculate additional per diem for payoffs that cannot be processed on MLK.