@Big_joe1 

Not a lot of info to work with.

Depending on how far the BBQ area is from the main router and things in between makes a difference  in how to set up your network.

if you can get a good wifi about half way to the problem area, a simple extender or router in extender mode if it has it will work most times. It would be slower than an Ethernet connected AP or extender.

you can connect your TP Link router to the main router (or to a switch connected to the main router) via ethernet and put the tp router in ap mode. Place the tp router in or near the problem area.

A MESH system can work in most networks however mesh unit placement is important. Best if all mesh units can connect to the main unit. If you need to dasiy chain them then speed will suffer. You would not need your old router with the mesh system.

there are power adapters that can be used to connect router and APs instead of an Ethernet connection. Can be a bit slower but does work when needed.