Hello everyone! My name is Samantha and I'm getting married in the Church in 13 days

I've been lurking here for months and you all seem so nice, but I've never posted.
I am trying to plan out how everyone will walk in and I need a little help. I have 1 grandmother and FI has 1 pair of grandparents. Should they be included in the processional? If so, what order? Who should I have escort my grandmother if she's in the processional? My brother will escort my mom and he is the best man, would it be ok to give him that job also? Also, who walks out first, my mother or FI's parents?
After the grandparents and parents, I'm going to have bridesmaid 1, 2 3 (FI's sister), 4 (FI's other sister) MOH then me and my dad. Is that good? I wanted to separate FI's sisters because they're twins and I want them to look like different people, but they are his sisters and good friends of mine (I met FI at the suggestion of one sister) so I want them to come down right before MOH.
Does this sound ok? Thanks for the advice!
Re: Processional question
your FI"s grandparents can walk together, and they shoudl come before your grandma. your grandma can be escorted by one of her sons or an usher.
the mother of the bride is always seated last, before the WP comes in. the seating of the MOB indicates that the processional of the WP and you is about to begin. its also a place of honor for the MOB.
i dont think it matters if you split up the twins or not. some have the ladies walk in shortest to tallest but there's really no method.
Do you know who will be running your rehearsal or do you have a parish contact? Some priests/parishes are particular about these details, so it would be a good idea to check with them.
FWIW, we didn't include any grandparents in the processional (in part because I had 2 in wheelchairs). It went 1) Priest (he asked to process, and we wanted him to anyway, but I know many do not process at weddings), 2) H and his parents, 3-5) pairs of BM & GM, 6) MOH and BM, 7) Ring Bearers, 8) FG, 9) My dad and me (mom is passed, but I probably would have included her if not).
For you, if all the guys are just "appearing," I would do this: Include the grandparents if you want. Get a cousin or and uncle (just in whatever they are wearing) or a groomsman to escort your grandmother in. Have the other grandparents escort one another. Have your brother escort your mom, have your FILS escort one another, then do the processional as you suggested in your OP. The guys doing escorting would just go stand in their place when they get to the front.
The order of BMs sounds fine -- it really doesn't matter as long as you're comfortable with it. I agree that I wouldn't have the twins walk together -- they aren't adorable 5yo flower girls, they are grown individuals!
I still have a little bit of time to decide.
My only contact at the church is my priest and as long as I'm going with what the church says, he's given me a lot of freedom in what I want to do. There have been very few weddings at my church in the past few years because of the pastor before the current pastor, so I think he is happy to have weddings again.
They are being announced together into the reception, but they requested that. They said they'd have more fun walking in with each other than with another bridesmaid and a groomsman. Whatever makes them happy!
If your FI's grandpa has this type of personality, he could walk with a lady on each arm! (your grandma and his wife)
I think it might be best if you walk with both parents, if you don't have an usher that could escort your mom.
I'll just echo others that the order should be:
Crossbearer, if you have one
Priest
Grandparents
FI & his parents
Bridesmaids & Groomsmen
Maid of Honor & Best Man
You & parents