AT&T Fiber, Frontier Fiber and others offer fiber in various areas in Houston. Check to see whether there is an alternate provider at your location, which may be less expensive.
If you need mobility and have an existing two-line multi-handset DECT system with an analog interface, getting an ATA may be a good idea. I’d recommend the Obihai / Poly OBi202 or 302, because it can do hunting with a single registration (incoming call routed to phone 1 port if it’s not in use, otherwise to phone 2 port). Although I’d prefer IP DECT, buying on eBay is iffy because most sellers have only handsets or only bases and it’s hard to be sure they will be compatible. The new stuff is expensive.
I personally gave up on cordless of any kind a few years ago, when I was ‘forced’ to carry my mobile at home (for SMS 2FA, WhatsApp calls, etc.) Given that, I just use a SIP app on the mobile, so I know little about current IP DECT. However, that may not be practical in your situation, if serveral staff must take calls (on different days / shifts).
I’m curious what kinds of calls you get and how mobility helps. I assume that people no longer call to ask when you’re open or how to get there. When someone calls to make a reservation or order takeout, I would guess that you enter it into the system right there. Likewise for outgoing calls (purchasing, problems with delivery, etc.)
A situation where mobility is useful: Guy calls asking whether you have bittermelon (苦瓜) tonight. You’re not sure so go to kitchen to check, come back to the caller and say sorry, we’re out. So now he asks, “Well, do you have pea shoots (豆苗) or ong choy (通菜)?”, and you have to go to the kitchen again. With mobility, you’d only go once. But better, if you have an intercom where the cooks can answer hands-free, you wouldn’t have to go at all.