agreement with compound subject, with an intervening prepositional phrase

I am struggling with a sentence, as in a condolence note:

Your kindness and friendship to both my parents [was/were] so special.

If I omit the "to both my parents" bit, then we have a compound subject that sounds natural with "were":

Your kindness and friendship were so special.

But when I add in the "to both my parents", my ear grates at the "were" and wants a "was" there. Which is correct, and what has changed?

I suspect that adding the phrase "to both my parents" in this way (without commas) creates an adherence between the "kindness" and "friendship" and effectively fuses the compound into a singular entity?