Is it ok for one parent to speak to an infant with more than one language?

Absolutely. Infants/children who grow up in 2 language homes will usually become fluent in both languages.
Its GREAT! If you can speak to your infant in multiple languages then you should! When we are born we have the ability to detect parts of language called phonemes. As we grow and don't hear certain phonemes, they disappear for us. By hearing phonemes of multiple languages, an infant can more easily learn these languages. I know I want my kids to know more!
A bilingual home. environment does not delay acquisition of either language in a typically-developing child, though the child may speak one language more fluently than the other early on. The problem comes when young children have a Receptive &/or Expressive Language Disorder. In that case, it's preferable, but not always possible, to do Speech/Language Therapy in one language & use that language at home.