I'm sure Eliot 1 will swing by Eliot 2 at varying points for idle conversation. He might be willing to introduce Eliot 2 to people should they be in each others orbit and he notice one of his friends? The "Have you met So and So" type of thing. Remus will make a point to introduce himself to Eliot 2, since Eliot is so important to Petunia. We should discuss how that goes because I am amused by the mental image. And Alice is flying this party solo so she'll be wanting to spen some time around your Eliot.
Eliot will be glad to see both Julia and Tony. Eliot isn't too familiar with Julia's drinking habits so that won't be a tip off for anything being odd to him. He'll just be pleasaant and happy in her presence as well as Tony's. As for Alice, well, she'll come over to greet Julia and Tony but that's largely because she wants to say 'hello' to Tony.
Eliot is going to be in a very good mood and very affectionate today. He'll come round and hug Fen from behind at least once and there'll be cheek kisses. He'll actually be being mindful and checking in on her to make sure she's having a good time. He'll even offer to get her food or drink like a semi decent husband. Remus will say 'hello' to Fen.