You are best to come up with a specific value and state that (or point to a card or something) when asked. Declaring the gift probably guarantees the traveler will be asked, so an honest and reasonable response should be prepared. This always happens to me as a resident when I check that box that says commercial items are with me (there's no minimum value so I almost always have to check it to be honest). They then ask what it is or what it's worth or what it is, usually cursorily, and I'm sent on my way, usually. Sometimes they randomly want to know more.
The agents are actually very experienced and will likely have a good idea of what the real value is, if they even care to look at it. Unless the person's language is rare, they they can probably get someone to help with communication.
What you would like to avoid, if possible, is a lengthy and stressful secondary inspection where all sorts of things could go wrong, especially if the traveler is stressed and has communication problems. Potential problems are more likely to be immigration related such as deemed intent to work without the proper visa (assuming the declaration was reasonable and complete).
If the gift does not appear to be worth more than a few hundred dollars, there will likely be no problem (ie no taxes), especially when it is clearly a gift and the person is coming from far away, as opposed to popping over the land border for a few hours.
If it's obviously worth $thousands or has some other problems (made of endangered spotted wombat hide or whatever) then I don't know what will happen. A semi-worst-case scenario would be being asked to pay HST (13%) on the assumed value of something that is admissible (or having it seized if it's not admissible). This is far more likely if it looks like the item might be for resale, and they are pretty good at figuring out if it's an artist delivering their work or whatever.
There is a separate customs system at the airport for commercial shipments, including a 'long room' where brokers (mostly) and the odd (definitely) person like me can clear shipments formally. It's possible for hand carried goods on an incoming flight to be moved to that system, and that might happen if the person requested a broker perform the clearance. It's quite unlikely to be more favorable than the treatment you'd get from the agent- and the clearance procedure is markedly more complex and geared for professionals. It's more likely to be because the value is high and goods are declared as commercial.
It's okay for there to be some range in possible value (provided it's not stupidly low like less than material costs) but whatever you do, don't coach the person to lie, that will really piss them off, and they could be refused entry, with or without a ban on future visits. They're really not out to collect every last penny of taxes from ordinary visitors to Canada- $60+ is where they want to know about it, not the threshold at which they will actually ask for taxes.