Alison is a definite no. Cindy is also a no if she and Wade are still taking a break. Louise and Ivy, I think we only get one or the other, definitely not both. Jeremy I honestly don't know.
I think with the Cindy thing, they'll most definitely still be on break, but I still put her in maybe cuz I can see a bunch of scenarios in which she does go. Especially since she should still be part of Ians friend group ( I know she joined it after she started dating Wade but still why would they cut her off).
Scenario 1 is she hears about it while hanging out with Ian and Perry and he blurts it out. She obviously is all about that white girl beach time and nags Perry to let her join. Another is Ian invites her while they're having their affairs, Ian puts in a good word and maybe raises Perrys suspicion level.
Another scenario is Emma invites her. Idk just seems in character for her.
Louise and Ivy may be mutually exclusive for Lena to invite. Or maybe if Lena is Louise's Dom she forces her to join Ivy to the beach. She might not even care that Ivy's there considering she's been begging for Lena to hang out with her more and of she doesn't go she'll most likely not see Lena for a few days.