I dont like airport outfits as a concept, as they generally involve an outfit of clothes you wont actually wear on holiday, and I believe my holiday clothes should work hard!
I tend to go for a stretchy dress with a cardie and trainers, with tights if it's cold in the uk (take these off in the aeroplane loos, it wont be cold when you land). Assume you will walk a long distance between being dropped at the uk airport and arriving in your hotel room, so comfy footwear is a must.
Dont wear a lot of jewellery, you'll only have to take it off for security checks.
I tend to go with a small cross body bag (that will be my evening beg on holiday), that holds phone, purse, passport and kindle, the a rucksack I can fit said cross body bag into if I need to. Given the distances you end up walking, dc2 has often been tired last few times weve travelled by plane and needed carrying, having free hands, not having to hold a bag is good.
Think about your outfit for coming home though, so many times I've left a hotel at mid afternoon when its roasting, and by the time we're all through to looking for the car at Heathrow its 11pm, fucking freezing and we're all in shorts and t-shirts shivering. This year I will be the organised mum with a bag of joggers and hoodies to put the dcs in on the plane (and leggings to go under sun dress for herself)