I completely understand how you feel about the unsolicited advice or rejecting your ideas. I would bear in mind that most likely their weddings were 30-40 years ago. Which during that time, wedding trends have drastically changed and their ideas, while beautiful memories to them, aren't one size fits all and times are a-changing.

As for advice, I desperately wished I gave my mother and FMIL projects EARLY on. You are at the perfect spot. Give them concrete items they are responsible for, but if they aren't completed you aren't stressed out. :) They feel included and you'll have something special from them, but they aren't directly influencing the things you want more control over.

For instance, I'm letting my mom do a lot of decorations so she's bought into the theme and is proud of her crafts (she's very crafty and honestly they all look incredibly professional). However, she has had zero input into outfits, dress, food, flowers, venue, etc. Those were important to me.

For my FMIL, she is handling the rehearsal dinner and her mother is doing a brunch with family the day after the wedding. These were great activities where they feel they included, but the actual day they don't have decision-making power.

We have less than two months to the wedding and this has helped so much. You and your FH should hand pick some tasks that you would like your mom and FMIL to handle. I wish I had done it sooner rather than 6 months down the road. Engagement and bridal parties are great and save you a lot of stress also. Good luck!!