As many others have stated, you generally should not bring up your continued job searching. Seasonal retail definitely helps, but rather than just work under the assumption that "everyone knows 1/2 the workers will be seasonal", if the subject comes up you should make it clear that you are currently planning on a seasonal/short-term job, assuming that the particular company really has seasonal hires.
However, a lot depends on the corporate culture. Some companies hire people for very specific positions and it is very hard to move from those positions except in a very prescribed path. For retail that might be:
- Stocking shelves (requires very little training)
- Cashier (requires more training and some aptitude for customer service)
- Customer Service
- Store Manager
- and then up into corporate management
In that type of company, it doesn't matter how much IT experience (or marketing or graphic design or any other specialized field that could be use elsewhere in the company) you have, you'll likely be on the standard path for a year or more, assuming you stick with the company. (You don't plan on sticking with the company, but it could happen.)
But there are other companies, particularly, in my experience, smallish companies (not "mom & pop", but perhaps 10 - 100 employees) where top management does a good job of recognizing talent and promoting it properly. This can include taking a stock clerk who has IT experience and moving them to the software development team (which in a small company could be: the old guy just retired, you're in charge of the web site and accounting software starting tomorrow), or taking someone with clear aptitude for sales and making them a salesperson, etc.
So keep your options open. Be upfront about your skills and objectives. Remember, retail, as much if not more than many other industries, depends on IT at every level. Retail might be just "seasonal stock clerk". It could also turn into an unexpected career twist.