Lol, sometimes we have to ask the questions ourselves. *smile*
You can wear pants, most people will not hold their more mature guests to dress the same as some of the younger ones. For example, you would not be expected to wear high heels, whereas a younger woman might be frowned upon for wearing flats. You can look at it as you're earned the right to wear what you like *wink*
In my opinion, a nice solid pant and top is good, try a nice silver gray or black pant suit, with a white or pink blouse underneath. A gray or black pant with a white/pink/off white top, some patent or matte black shoe, and tasteful jewelry, is perfect. The simpler the better. Since spring is here, a tan or white pants set is nice as well, in silk or linen, with a fancy white sandal. You could also try a pin stripe pant with a button up blouse in white or gray. Pin stripe is always fancy.
Putting your hair up in a fancy style, with a nice comb, pin, or clip, adds to the look.
Above all, you should be comfortable.
I hope this helps, let me know if you need more ideas or want to give me any additional info.