My family of 5 is looking to go early to mid September. If you have any insight, I’d appreciate guidance! 
1 - When is Haunted Mansion typically closed for holiday decorating? How long is it down?
2 - How much is G+ if you buy day of vs when you buy the tickets? Or, what is the range at least?
3 - Is there a way to check a la carte pricing for Lightning Lane rides?
4 - I heard character autographs had stopped for a time due to Covid; are they back to signing?
5 - What are the chances of 2 WoC/Fantasmic showings on weekdays in September?
6 - I want all the things! But I need to be reasonable. I’m pretty set on spending the $$ to stay on property just for the early entry. If we’re getting that, how important is G+? I’m looking at crowd levels guessed in the 3-5 range right now.
7 - We’ll have 3 days; I’m assuming 2 days at DP and 1 at DCA. How important is Park Hopper?
8 - Are MagicBands worth it? My husband, two oldest kids and I will all have phones. My youngest (9yo) will not. Would it make sense to just get my little guy one? (It’s his first visit.)
Welcome! I’m not well versed in Disneyland but I’m following along! We want to do a trip in a few years to DL. These are all great questions that I have thought about as well!
Following…
Welcome Lissa! What a fun trip you have & you’re way ahead getting plans started 
1- Haunted Mansion will close mid-August for about 3 weeks. They usually try have it up by the Friday after Labor Day weekend (some years they do get it done the Friday of Labor Day weekend though as they’ve inched Halloween season earlier).
2-G+ is $25/day when you buy it in advance and you must buy it for all days. That is the lowest price you’ll see and we don’t yet know the ceiling (and I haven’t since they started this variable pricing to see if there’s been days more expensive than $25). If you’re certain you’ll want it all 3 days, then it’s easiest (and will be the cheapest) to buy ahead of time. If you’re iffy on if you’ll use it all 3 days, then you can wait & see (and try to track prices to see what the upper ceiling could be.
Early-to-mid September is a less crowded time so I don’t think you’d have to worry about it being astronomically higher than the $25/day).
3- The a la carte pricing will range from $7-$25 per attraction per ticket/pass. You’re limited to 2 per day between both parks. You can check daily on the Disneyland app under the Genie+ section without having to buy anything. There are some sources that will also track those prices too. I follow a blogger on Facebook (GothicRosie’s Disneyland Info Page) who does really detailed & visually appealing slides with all the info possible you could want for DLR. And she does a post with slides just for the daily prices for Genie+ & a la carte or Individual Lightning Lanes (called ILL for short). But there might be a better data focused outlet somewhere else like Thrilldata?
4- Character autographs have come back! We waited to do any character dining until end last summer and they had them back by then. I’m pretty sure they had it earlier too, but we weren’t yet comfortable doing such close interaction before then, so I’m not sure.
5- Looking back at the historical showtimes for last year’s showings they did have 2 shows/night. I would just make sure you look out for when they announce Halloween parties as the nights they do a Halloween party will impact the hours at California Adventure as the party will start at 6-7pm (and non-party guests will have to leave) & there won’t be a World of Color that night.
6- With early entry just being 30 minutes and really only giving you a jump on 1-2 major or 2-3 minor AND short attractions in that time, the better value by far is buying G+. BUT with the less crowded time of year that you are going, you may not really need G+ especially if you want to pivot from doing only rides during the busiest of the day (midday from 11-4pm ish) and focus on seeing some shows/walkthrough attractions/diversions that don’t ever, even when busy have more than a short wait, if any at all. For on-site, it’s a pretty penny and if it’s a trip you won’t be able to do again for years and/or, then I am all for splurging for it. We personally prefer to go frequently and save on the lodging by staying at offsite/Good Neighbor hotels.
7- Park Hoppers- They are definitely so pricey so I get using this as a way to reduce costs and it can be done. But the parks are SO close and hopping isn’t hard to do at all, so I cannot imagine not being able to hop. I would pay attention to if your dates will coincide with any Halloween parties and if so, make sure you DCA day is a non-party day.
8 - We have yet to find a really good reason to get MagicBands since they deployed at DLR. We did the very old versions at WDW when we went in 2016 and they were fun, but not necessary. And at DLR they scan the Magic Band on their handheld scanner anyway instead of a dedicated “tapstile” like at WDW so it’s mainly just the easy of everyone tapping for a LL one by one vs. scanning in with a phone (and one person can open up the app with the LL’s and scan everyone in one by one by swiping over). It’s a little slower, but they have your group stand to the side while you swipe everyone in & once the last one’s in, you all go in. That said, if the little guy will want to tap in himself, it might be worth it. There are some small effects that coincide with your location and the MB will light-up/make sounds that are a bonus addition/complement to some rides and also nighttime shows. So it’s really down to what your family prefers and if that’s something you want to spend money to have.
Anyway, hope it helps & happy planning!
Great info!!
You are my hero! Thank you so much for all your input. I really appreciate it! 
Agree that G+ and PH are both a better use of money than MBs. G+ has gone up to $30 during Christmas break and Presidents Day weekend.
If your touring style is “experience everything once” you might want one day without G+ to focus on the smaller attractions. However G+ also includes PhotoPass, so if you enjoy having the family pics it may be worth having one person in your party buy G+ in advance anyway.
Thank you for all of the great information. My BFF and I are heading to Disneyland in September too. I haven’t been since 1992!