I couldn't narrow it down beyond mid Jan to mid Feb. Give the folks at the Wickaninnish In a call - they are very helpful. And it's a great place to stay.
You might want to check out flying into Vancouver BC renting a car there and doing the ferry to Nanimo then across to Tofino - you can't drive from Victoria to Tofino along the west coast.
To extend Tim's response, there are two ferries out of Vancouver to the island. One leaves from Tsawwassen, which is SW of Vancouver and goes basically to Victoria (just north of Sidney). To get from Victoria to Tofino by road you have to drive north up the east coast, past Nanaimo, and go west from Parksville to Tofino. There's no road along the west coast. The other ferry leaves from North Vancouver and goes to Nanaimo, which cuts off an hour + of driving time, but you miss the drive along the way, including Duncan and the Cowichan valley. Depends on what you're looking for. The road from Parksville goes through Cathedral Grove, and you'll want to stop there.
And yes, mid-January to February is a good time. If you want, check out a weather satellite that shows storms happening in the Pacific and tracking east. Landfall comes first at Tofino and thereabouts. The Wick Inn is great but on the expensive side. There are a number of B&Bs and other hotels, but not all of them are open in winter. If you're into surfing, bring a wetsuit 'cause the waves are big and the water is cold. Of course you can also take the boat tour north of Tofino to Hot Springs Cove, if that's more your style.
Mike.
