They are direct objects, so use direct object pronouns:
In most of Latin America, les here is considered nonstandard (leísmo). You might hear Le/Les invito in Spain or as polite leísmo, but los/las is the recommended choice.
Spanish simple present can describe a present speech act or a planned/fixed future when a time is mentioned: Invito… el viernes = “I’m inviting them (to Friday’s concert).” Alternatives: