I'm nearly finished with a bench for the dining table in our sunroom, and have some questions around affixing the seat and back rest. All parts are poplar.

The back rest is 1.5" thick x 6" wide x 7 feet long, and the seat is 1.5" thick x 12" wide x 7 feet long.

In both cases, a 1/4" deep dado in the back rest / seat will fit snugly over the back support / seat support.

My concern is that if I glue the dado connection, wood movement will cause problems over time. So I'm instead considering drilling oversized holes through the back support / seat support that would allow fasteners to move (and then I would plug over those holes).

Am I being too worried, or is this the right approach? (or is another approach preferred?)

Thanks!