Update at the bottom

My baby sister got engaged this past weekend. I'm told my invitation is being sent. Evening wedding. In August. Of this year. 3 months from now.

I have enough sense to know that evening wedding means way more formal. I'm slightly panicked, because I have nothing to wear to a wedding unless it's a goth wedding or something.

Here's the complicating factors:

1. My sister is an ordained minister who runs the youth programs at a megachurch in a suburb on the north side of Atlanta Georgia. So it's in an area where people will definitely be well dressed, and it's definitely going to be attended by people she works with and leads in the church. I have to be situationally appropriate. (I was very inappropriate for all the years before I got sober, so I want to get this right for my family.)

2. I have a very large tattoo on the side of my calf. My family doesn't say much about it, but they really don't like it. So it needs to be covered, because my sister's wedding is NOT the time to "be myself", it's her big day and I can be respectful enough to cover it.

3. What the hell do I wear? I don't want to buy something that I'll never ever ever wear again if I can avoid it. I don't like dresses, it's an emotional comfort thing I guess. I'm ok with a maxi skirt, and I've been eyeing these silk taffeta ones on etsy that I won't mind having in my closet but I don't know how much I'd actually wear it. My mom says nice pants would be ok.

Am I really ok wearing dress pants to an evening wedding? Am I going to have to spend a fortune on something that I might not ever wear again? If I CAN wear pants, what kind? A tuxedo style, wide leg, slim fit, what?

I'm only about an hour and a half from the Dallas metroplex area and the wealth of shopping it contains. There's Park Lane; with Saks Off 5th, Nordstrom rack, and Bloomingdale's outlet. There's also a Last Call in Allen tx, and I'm pretty sure all of their full price relatives are around here too. There are also some amazing consignment shops that I could go to. So I have a lot of places I could start searching through...

But I need to know what to look for. I need to know if it's ok to wear black (on bottom) to this evening wedding, and what to look for on top. I also could use some pointers on shoes. I'm only in marginally better shape in the shoe department. I have some Ferragamo nude suede pumps with a mid-height heel, I have some Stuart Weitzman strappy sandals, white, with these cool grommets on the straps, with 5" heels, and a couple of pairs of black ankle booties that probably have a bit too much rock-'n'-roll or goth or something going on.

It's funny I'm having to turn to the internet for image consulting after the discussion we've had on here about the crowd sourced internet based image consulting recently, but y'all are the trusted friends that know their stuff when it comes to dressing appropriately.

So I'm clueless and panicked, please help. Any tips/suggestions/pointers are welcome from Angie or anyone else that has ideas. I'm ok with being shown really expensive garments for inspiration even though there's no way they'd be in the budget while we're trying to build a house without taking out a mortgage; because they'd definitely give me inspiration and some styling cues.

EDIT/UPDATE:
Just got off the phone with Mom. She says yes, it's an evening wedding, but it's not formal formal. Mom said maybe semi-formal? The bridesmaids are wearing short black dresses, the groom & his two attendants are wearing black suits--not tuxedos, mom is wearing floor length (in steel blue) and IS WALKING MY SISTER DOWN THE AISLE which is so freaking awesome that I'm all crying over here...
If my dear Sunshine were to attend, he must wear a suit. An actual suit, not trousers and sports jacket or anything.

Mom kept suggesting "those flowy pants, satiny like material, they're really popular right now" which I am assuming​ is mom-speak for Palazzo pants. She said a nice dressy top, and she was very grateful that I was definitely covering my tattoo and wanting to just blend into the crowd so my sister could shine.

My mom also laughed at me when I said I was asking for help in a fashion forum led by a professional stylist. She said "Cindy, you know how to do this". I had to remind her that it's been a lot of years since I've tried to "dress up" because my life has been so very casual and my tastes have gotten more unconventional with each passing year. She's right that once I would have been confident. Maybe I'm just feeling the weight of (self-imposed) responsibility to get this one right, maybe I am a bit out of touch with more conventional dress codes. Whatever, I've got y'all and y'all have got my back, and I'm grateful as can be.

So, Angie, semi formal (I guess?). And I confirmed just the one event, I am not expected at the rehearsal dinner. I will probably be traveling for a few days, with airplanes involved which means slip-on shoes at the airport LOL.

Again, thank you all for your help!