Nobody has mentioned beer/wine so far, or spare batteries. Gas cooker? Matches and/or lighter. Spare gas canister too (keep a jet boil in my van, just in case).
What keeps the little one occupied? Paper, pencils, crayons, games etc.
Most of our gear goes into ikea bags. We never bother with quilts, way too bulky, always sleeping bags and liners. All sleeping gear is put into one of the giant bags used to cover a rucksack when flying – the bags are cheap, huge. My wife always wants her own proper pillow too.
We started with a T4 almost 20 years ago, also had young daughter and a dog to accommodate. Best significant purchase ever, but couldn’t afford new now. She’ll be getting a van herself in the next couple of years.
Enjoy