Weighing pros and cons for using jQuery for just one widget

Question

I have been using html select boxes or textboxes for date input. On submit, the date is validated and if invalid an error is returned. I have avoided javascript calendars thus far, but jQuery datepicker seems to be a popular choice amongst people on SO. I was updating my app and wondered whether to use a Javascript Calendar(jQuery datepicker in particular). It would be a good "feature" for existing users and will fit the "2011" upgraded look of the app.

I am not using jQuery or anyother JS library. The scripts in use are "plain" javascript. With jQuery, I will have to include jQuery's library in the universal .js files list or link to Google's copy. Either way it will increase page load time. And I understand that with or without datepicker in place, the validation(and the error handling) stays and that the datepicker widget is for visual purposes only. But UI is an important factor.

A positive that I can see is, I might use more of jquery in the future and I will not have to think about page load time and bandwidth issues then.

So my question is, is lugging along jQuery the right decision, when I only see one use in the near future? Or should I use a "plain" JS only calendar widget or should I simply stick to the select or text boxes.

_{Wanted to post this on SO, but since the topic is more about programming practices and decision making, I am posting the question here.}