My recommendation is to choose one (or two) persons who function in the team is primarily to be the HR/Onboarding specialists that mostly just interact and RP with new recruits to help them integrate with the team. The RP could revolve specifically around this. "I know you guys are new, and this is all pretty overwhelming, but I'm gonna help bring you up to speed and trust me, you're gonna fit right in. You have any questions, you feel unsure about anything, my door is always open; just shoot me a DM over HeroBand, etc..."
These people got all the dish on the SG, probably because they've been with the group since it's inception. Maybe like to share gossip, explain history of the team, answer questions regarding past exploits and what not. Also, in this vein, they should reassure new members IC'ly, that they understand the team has a long and storied history, but you don't need to feel like you have to learn the story of every battle we fought and memorize the names of all the members the first day. Just be patient and hang in there. You'll have plenty of time to get to know everyone as we train together. So on.
Of course, some players will just not feel comfortable integrating into a large group with a long history. These players are better suited by looking for smaller and/or newer groups, with less established lore.