I saw you post this dress before, but now I realize this is the same gown my best friend got married in! I personally would not add sleeves to this because all the floral appliqués are very detailed and it could be hard for them to make sleeves that match well.
I would leave the address as it is. I think adding sleeves will make the dress look heavy and may make it too hot for a Spring wedding.
Look up “wedding bolero” it’s basically a tiny jacket with sleeves that you can remove. This may be a good option for you instead of altering the dress?? Just a thought but I think the dress is gorgeous on you as is!
See if you can find some nice lace applique sleeves that you can just slide on and up your arms, so later you could easily remove them to give your dress a completely different look. Getting the effect of changing to another dress without the huge cost of it.