You’re definitely right to send a thank you note for the gifts from them now - I’d just focus mostly on the gift and maybe add “we hope to see you at the wedding” or something else that indicates you’d be happy to see them but don’t necessarily expect it.

For people who do attend, if the gift comes pretty far ahead of the wedding I’d send the thank-you note as soon as you receive it, but if it’s close to the wedding (often people say within 2 weeks), you can just do one after the wedding that mentions both the gift and their attendance. And yes, shower gifts would be a separate card.

We used these cards, but there are tons of other cheap options on Amazon and similar to go with whatever your aesthetic is.