Q: We are only having one mass on Aug 15th at 6pm. We have a Communion Service at 8am on weekdays. Is it acceptable to still have a Communion Service that morning?
A: I would say no.
The Sacred Congregation for Divine Worship issued a Directory for Sunday Celebrations in the Absence of a Priest in 1988. Paragraph 21 says, “a gathering or liturgical assembly of this kind can never be held on a Sunday in places where Mass has already been celebrated or is to be celebrated or was celebrated on the preceding Saturday evening, even if the Mass is celebrated in a different language.”
I would apply that to holydays as well.
A better solution is to make the 8 am communion service a Mass on that day.