I think the filmakers smartly left this open to interpretation, but playing it more on the safe side.
My interpretation is that they did not have sex. There just wasn't any real indication of that. I think Saavik simply helped him center his chi. (Is that what the kids are calling it these days?)
Wisely is right because that kid was a minor....and Robin Curtis...well...wasn't. I don't like those implications so...I'd rather believe his chi was focused (That's what she said)