Hello! I'm getting married on Maui this October, and we visited last October to do some site visits and planning. We went to the Ritz as well as Kaanapali Coffee Farms, Westin Villas, and the Sheraton. We also considered Merrimans but never visited it. In the end we chose the Sheraton, & we're very happy with our choice! Their grounds are lovely, they aren't outrageously expensive, and it's a great location. I strongly recommend you consider it! We're having 40-50ppl for reference.
We're getting married here: http://www.sheraton-...venues/moanalaw and it's even more gorgeous in person! They don't have that ugly white fence anymore either which is great. When we were there, there were dolphins jumping in the water right below this venue. It also has an attached (air-conditioned) lounge that you can use for cocktail hour or a reception if it's a small wedding. Then our reception will be here http://www.sheraton-maui.com/weddings/weddingvenues/coralreefroom which again is a gorgeous space. We chose this for the reception because it can be enclosed & air-conditioned (Not sure when you're getting married, but it might be one thing to consider) and you can also have your reception last until midnight (we even talked them into 1am). You may already know this but if you're planning to have your reception outside, you can only do it til 10pm, it's an island regulation. So, this was a big part of why we went with the Sheraton & the Coral Reef Room, because if we're spending all this money for our big day, we want to be able to enjoy it all night!
Back to your original questions. The Ritz was gorgeous of course, & I would still love to have my wedding there, but it ended up being too pricey for us. I don't remember everything exactly, but we were looking at $18,000 for the ceremony & reception spaces & the base food & drink prices (based on 50ppl I believe). So that didn't even include decor, or drinks beyond wine/beer. etc. At the Sheraton we are paying about half that. If you do want your reception to go later they have one ballroom at the Ritz that you can use past 10pm.
Now for the wedding planner. We are using the lovely Taryn Wyant of Platinum Weddings & Events http://platinumweddingsmaui.com/ She has been nothing but fantastic! We met with her in person while we were there, she showed us the Kaanapali Coffee Farms, and gave us a lot of great insight. Since we've been back in the states she is super quick to respond to emails, calls, and texts, and will happily tell you detailed information & experiences with all the different vendors so you can be sure you'll make the best choice. Just today I was freaking out a bit about if i'd made the right decision on a photographer, and she was very understanding and helpful. I hope that you'll take my word for it and get in touch with her, I don't see any way you could regret it! Bonus points, should you end up liking the Sheraton, Taryn was the one who started their wedding program and ran it until she left to start her own business, so she's very familiar with the property & many of the staff members. I should also note that we liked the Sheraton before we even met with her, so she wasn't getting a kickback to promote it or anything.
I don't know much about Merriman's but I do know they have the 10pm curfew as well, and I think Taryn told us it could be a little small & crowded. Of course that may not be an issue if you're having a smaller wedding.
As far as wind, I've heard the same thing, that certain areas are windier and then that the whole island is windy, so who really knows! I'm just hoping it won't be too terrible on my wedding day.
Sorry this was so long, but I hope it's somewhat helpful! If you have any questions feel free to message me! I'm excited there are a couple more people in the Hawaii part of this forum now