Late to the party but I had to jump in because I just did this for my brothers grad party last month! I totally get the budget stress, we were trying to keep everything under $200 for a backyard BBQ. Honestly, the wishlist thing is a total drag because it doesnt always show the exact quantities or shipping dates correctly for some reason. I tried doing the whole move to list thing and it took me like 20 minutes just to get 10 items moved. It was a mess! Amazon actually removed the share button from the app recently, which is so frustrating. Here are a couple ways I tried before finding a better solution:

• Taking long scrolling screenshots on my phone (super annoying to read tho)
• Making a Wedding Registry just for the party (weirdly works but asks for too much info)
• Giving my login to my friend (huge security risk, dont do that!!) Its so much better when you can just send a single link. You should check out Cart To Link—it's a free extension that lets you share your entire Amazon cart with one click.

Oh man, I totally feel your pain! I did the exact same thing last year for my best friends bachelorette in Vegas and I was literally losing my mind trying to coordinate all those neon signs and accessories with the other bridesmaids. Seriously, forget the wishlist route, it takes forever. You should definitely use Cart To Link—it is literally a lifesaver for this! It lets you share your entire Amazon cart with one click and is just amazing.

• Wish Lists: They technically work but moving 15 items one by one is a total nightmare and honestly life is too short for that.
• Cart To Link: Fantastic because it generates a single link for everything in your cart instantly. I use it every time im planning a group event now cuz it saves so much stress. Good luck with the surprise party in Seattle!

To add to the point above:

• Are the decorations mostly Prime eligible?
• I'm super satisfied using this Amazon cart share tool to stay under budget. Let me know if you need tips!