I have to agree with @computer_freak_8. 10Gbps switches are going to be out of the price range for a church with 120 weekly attendance, and very much overkill. I would say that a decent layer 3 core switch has helped our small church. Scrap the idea of redundant switches entirely.
The other thing that you don’t mention is ongoing mgmt of the network. Are the trustees going to take care of it or will you? Either way, you’re going to want something easily manageable. Like @OneSeventeen said, I’d keep it all the same brand where you can. Ubiquiti has switches and APs that all tie into UniFi and make management and deployment so much easier and allow you to tie into a cloud controller later. They are affordable considering what you get. Ubiquiti doesn’t have great UTMs yet with content filtering and malware blocking, so a lot of smaller churches will still go with SonicWALL or they will take advantage of Cisco’s ASA discounts provided for churches through TechSoup (if it’s available to them, see below).
How many switches do you need? We have two servers (we also have a RPi for monitoring and a PBX, but I don’t really count those), we’re running VoIP and IP Cameras, desktops, APs, and network drops to each classroom. Our space is larger than yours and we get by on two 48 ports switches in our main closet and an additional 24 port PoE+ (of which we have 5 or 6 ports used) at the front of our building for cameras and APs.
My 2¢: Honestly, for your capstone, it may be better for you to design a hypothetical campus network with several buildings on a main campus and one remote campus that’s a single building or something. It sounds like what you’re designing won’t help the church you’ve selected, but rather send them into massive, unnessaccary debt.
If you’re set on this church being the subject of your capstone, I recommend getting a better feel for both what they need and what they can afford. Network design is never about getting the best possible everything for anything of any size regardless of cost, but rather balancing a budget against needs and wants, and designing a network that affords elasticity, manageability, and upgradability. Hopefully your professor agrees that a large and complex network diagram with all the bells and whistles is less valuable than a real world implementation with a budget and needs that are being met creatively within that budget. Good luck!