We just upgraded to smartphones as well. It sounds like you have 3 people you need to upgrade for so why not get a mix depending on what people want? I’ve noticed for women, they seem to LOVE the iPhone more as a status/fashion symbol and because everyone else they know has one. I would recommend you watch these series of videos to get an idea of what iOS and Android can do. My wife went with the iPhone and I went with Android and feel like I can do a ton more than what she is using.
It’s sorta like the PC vs Mac debate. If you are pretty tech oriented, you probably would like Android more being a more customizable option.
If your wife is happy with iPad/mac, then maybe she will be happier with that than forcing her to use Android.
Costco doesn’t sell iPhones anymore so you would first need to decide on provider, then go from there…