Can anyone tell me the best way to handle our database?

I will give some background. I started using Microsoft Access. This worked great for many years. I had forms etc. When and address changed I would update manually. Well the one time we sent 18,000 mailers and like 3,000 needed to be update. I did this once but lost the will to do again. We then went to Excel. Excel works but it does not have all of the other info that Access had like did they pay dues etc. and it is hard to keep a Master file updated. Here are my thoughts -even though I know little about this- I would like to create a Master file online so that committee Members can make changes online. If we did this on CC we would have to add like 9,000 address. I doubt that would work. gotta be an easier way.

You have a database that is large enough that it probably should be in a "true" database system. One solution is Caspio. It is a cloud-based system that uses MS SQL Server for data storage and allows forms, views, reports, graphs, etc. to be easily developed and placed in a Class Creator (CC) page. The free version has some limits but it gives a pretty good idea of the product's capabilities.

Another potential candidate would be a WIX data collection. It doesn't have the same feature set as Caspio but I've seen some rather large data sets produced. It too can be linked to CC pages. You can sign up for a free WIX account and give it a try.
Here is a sample form from WIX Your text to link here...

You are able to download all of the data, including any updates the committee members or the classmate themselves have made, into one large Excel file. Class Creator gives you the option of picking and choosing which pieces of the database you want to include in your Excel download; name and contact info only, or every possible piece of information including any profile questions they may have answered. You can then use this new Excel download as your Master database/spreadsheet, or you can do a copy/paste and add it to your existing Excel spreadsheet as a new worksheet tab. You can then do a VLookup or some other formula and identify what data is new so that you can bring it over to your Master spreadsheet.