I love my REI brand tent, which is a much older version of something like this:
https://www.rei.com/product/227863/rei-co-op-campwell-4-tent
Mine has been going strong for over 30 years, and I've abused quite a bit it along the way. If you are camping twice a year, one night at a time, at established group sites (I assume this is Scouts?), a less expensive brand is just fine too. Lots of our campers use Coleman tents and they work well.
Mattress pads:
Kids may not need them, or are OK with something inexpensive. One of my kids has always used a folding foam eggcrate pad, the other ignores all pads and puts his sleeping bag directly on the tent floor. My 47-year-old back, however, does not appreciate such treatment. I like a nice, thick, battery-powered air mattress. If it's cold overnight, the pad adds insulation from the cold ground as well.
I have a 30-degree sleeping bag. If it's actually going to be below about 40, I add an extra layer to it and wear a hat while I'm sleeping - I run cold.
You can take pillows from home, no need to buy "camping pillows" unless you start backpacking.
Do have a flashlight or headlamp for each member of the family.
Camping chairs: REI options are great but expensive. Dicks has good options. I like something basic like this:
amazon.com/Amazon-Basics-Folding-Mesh-Back-Carrying/dp/B074YRN643/ref=sr_1_1_ffob_sspa?crid=9J06YVGSSPHB&dib=eyJ2IjoiMSJ9.Tpi-BmwXhIv3wR4mn0e0sjKeK1vwEOy8JQFljeZ4egoqkhzVHlCOnIgLWTjxEC-6MyaCz48lGf71ngfsyu93ZKi1QkVkVelOYjNb8NaUYStO-bl11YZHczhbQk0cqnCrsxXvCDUARTY0WU54MfbTu8NOG20W0fbZ3WcZj93nNIhF4OiI-j5I9fqPNpxfnQxHfvfqbqS_r0iHVqw70jTW80tmU6kzS3ieINqH3qH-HopfI9VxLr0I2RMUsLtwG1tYZcFYSc5oZC9khBCrGUojTEmz1EjLZlscgWHkkVngF1w.mj5YxV40sJhnDTHupwZ52hJC4_LWas4-UCqb-6ngIEE&dib_tag=se&keywords=camping+chairs&qid=1757010531&sprefix=camping+chairs%2Caps%2C117&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1