A dress up box is a gift that keeps on giving. Kids LOVE them. Old costumes, funny clothing from the thrift store - particularly sequins, bridesmaid dresses, crazy accessories (giant sunglasses, a purse, etc.), sparkly shoes, Halloween costumes, etc. Dress up boxes are also great because they are something kids can play with pretty independently and also tend to enjoy for years (e.g. 2 year olds like them, 6 year olds like them, 8 year olds like them...)
Same with sticker books - loved for many years, takes up little space, kids can do on their own.
Ditto recommendation for gift cards to events - you don't have to attend. Just get a giftcard for the movies for the family
I would add that play kitchen stuff is hugely popular with preschool age kids. You can find small size pots, pans, plates, etc. - likely at thrift.