I think using the RH sign and intervals would be acceptable. You may want to include a quick TN if this is the first (or only) time it will be used. But I'm imagining this might be at the start of the piano method book in which case introducing the hand signs would be appropriate.
If however, it's part of a book for a single line instrument and intervals are few and far between, using an in-accord may be clearer. (I'm partial to piano format when piano music occurs, but it really is a matter of context.)
Hope that helps!