If you had asked in September I would have said to go for it at that price. The holiday season is prime time for photography.
At this point your ad would be coming out too late to allow people to be guaranteed delivery in time to give as gifts.... or maybe not, I don't know what you're turn around time is.
This late in the year I'd target existing customers. Maybe a holiday card with some coupons enclosed:
1) Order photos from a previous session at a discounted price (for customers within the last 6 months or so)
2) A good deal on a new session (for all customers)
3) A free gift (an 8x10 or something) when they refer a new client. (Make sure the client actually comes in before giving the gift!)
A roll of stamps would cost... what?.... $42? Ready to print cards are available at Office Depot for I don't know how much. Print nice copons on your computer. You could probably send out close to 100 with your $100 budget.
Otherwise I'd save your cash and start thinking about a Valentine's Day promotion.