Have you ever had a client come to you in mid-November wanting to take the family skiing over Christmas, or to the Caribbean? 
After an understandable immediate thought of "Are you kidding?," I hope you inquired as to flexibility of travel dates, destination and budget, and learned what would be necessary and not-so-necessary in accommodations.
The more flexible the client, the greater the possibility of your being able to put together a great vacation for him or her, even under these circumstances.
Sure, there are some resorts and some airline routes that will simply be sold out at all classes. But you might be surprised at what is available.
Taking the Time
Of course, a last-minute peak-season travel request, especially for a family, will take time to research. You'll have to be resourceful, creative and persistent, and use your contacts.
You might have to pull out a map and see what areas are close to the one your clients are looking to visit. Or, if they're open to, say, skiing in the west, get on the phone with a number of different lodges —and if you're lucky enough to find an opening, find out if you can get your clients there.
You might need to look at lodging options such as villas and condos, and to route your clients creatively, or see if a private flight might be a possibility.
Now is the time to be persistent and not to take "no" for an answer from the first person you speak with, or be discouraged by seeing no availability on a web site or GDS.
Especially if you do a good amount of business with a hotel, and/or have a relationship with a sales rep or GM and/or your clients have a good budget to work with, you will have an ace up your sleeve.
Is all the effort worth it? The answer depends on the client and your workload. Is it a longstanding client? A VIP? Do you have the time to put this trip together without damaging your relationships with other clients?
Learning From Experience
In June, my fiancé and I decided we'd get married in July. The priority was putting the ceremony together, going through pre-marital counseling, inviting guests and putting a small reception together. Oh, and moving in together. And putting gift registries online. And, and...
This meant that the Monday before my Saturday wedding, I was seeing if I could spend the next week on Nantucket. In nice places. In the middle of July.
Lo and behold, it all came together. We had to move hotels each night, which wasn't ideal, but we did get to experience different parts of the island. And due to new flight service, we got airline seats without a problem. So, you never know until you try. 
Anastasia (Stasha) Mills Healy Managing Editor [email protected] 212-895-8251