There are two ways to interpret that sentence, and it hinges on a weirdness of how English uses the indefinite article.

Any character or monster that doesn’t notice a threat is surprised at the start of the counter.

The usual interpretation of "a threat" here is that it means "one threat". If that is the correct reading, your question is the result. Is it correct though? This meaning would require that surprise is a relationship between two individuals, so that the dire wolf could be surprised by the rogue but also not surprised by the enchanter.

Is this how surprise works? It turns out, no:

If you're surprised, you can't move or take an action on your first turn of the combat, and you can't take a reaction until that turn ends. (PBRv0.2, p. 69)

Surprise is not a relationship between two entities, it is a state of a single entity. It's impossible to be surprised by one opponent but not surprised by another.

Is there another way to read that sentence about "a threat" that makes surprise sensible as a state? As it turns out, yes.

"English is funny that way"

Another use for the indefinite article, which looks identical to the "one threat" meaning, makes the sentence in question

Any character or monster that doesn’t notice a threat is surprised at the start of the counter.

mean any threat at all, not just one. If this meaning of "a threat" is how it's being used, then that means only creatures who notice no threat are surprised.

Because this reading is perfectly normal English, but ambiguous, we need to confirm the reason by looking for clues in the surrounding text. That confirmation is in the definition of surprise we looked at above: being surprised means being completely surprised, which only makes sense if it happens when no threat is noticed.

So the dire wolf is not surprised, because it did notice a threat, as opposed to not noticing a threat. (See how that makes sense put that way?)

On the plus side, the champion and the rogue don't need surprise to have advantage on the dire wolf, because that doesn't rely on surprise, but rather on being unseen, and being unseen is a directional relationship, not a state.

No

According to the Stealth skill:

When moving at a speed greater than half but less than your normal speed, you take a –5 penalty

Being Observed If people are observing you using any of their senses (but typically sight), you can't use Stealth. Against most creatures, finding cover or concealment allows you to use Stealth. If your observers are momentarily distracted (such as by a Bluff check), you can attempt to use Stealth. While the others turn their attention from you, you can attempt a Stealth check if you can get to an unobserved place of some kind. This check, however, is made at a –10 penalty because you have to move fast.

This fast movement is to take advantage of the momentary distraction offered by the Bluff. As it does not specify you are able to move your full speed without penalty, If you you chose to move over half of your speed, you will be making the check with a -15 penalty.