The font or typeface you use is ultimately up to you and the style of your wedding invitation. If your wedding theme is classic or traditional, you should probably use a cursive or script style font. If your theme is modern, a simple plain font such as Arial or Helvetica would work nicely. Blackletter fonts work well for medieval / castle type themes. Serif fonts (like Times or Times New Roman) work will for Old-Fashioned theme weddings.
The typeface of your wedding invitation is such an easy thing to change. Try different typefaces on your design until you find the one that looks just right.