How should I ask my bridesmaids??

I don’t have a lot of female friends. A couple I am very close to, and a few more that I am not as close with. I have seven ladies I would like to ask, but only three I am positive will accept. I know it’s traditional to put goody bags together for bridesmaids or find a special way to ask. Given that some of these friendships aren’t as close as others, would it be best to approach them casually about it first?

Or just surprise them with the goody bags I had in mind? I don’t want anyone to feel pressured with the gifts.

What is the best way to go about this?

*for clarification, I’m asking seven because my fiancé has his heart set on asking all seven of his friends.