Jay answers: Congratulations on starting out on this new adventure together! I think you two are about to have a lot of fun!
Before you head out into the world of meet-ups, hook-ups, and on-line connection apps, this is a good time to do a lot of talking about what you and your partner want this new adventure to look like. When you say you're opening your relationship, it's important to make sure you're both on the same page.
For example, are you planning to date other people romantically either separately or maybe as a couple? Are you looking for more casual hook-ups? Are you hoping to arrange some threesomes? Are you okay with watching your partner have sex with another person in the same room with you or would you prefer they have sex with someone else behind closed doors?
The term "open" gets used a lot and can describe a lot of different scenarios. Before you go out and do this, have this conversation with your partner to make sure you're both looking for the same things, that you're both picturing the same scenarios.
Also on the topic of preparation, I've written before about opening relationships. Past blog posts have included Ideas to consider when planning to open your relationship, Attending kink or swinger events for the first time, and Getting out and meeting new sexy people. This last article on meeting people will likely be the most useful in terms of connecting with like-minded people who want to join you in your new, open dynamic.
You asked specifically about connecting with people without outing yourselves. The good news here is that if you're connecting with people on websites such as Swinging Heaven, FetLife, and Adult Friend Finder then the only people you're going to encounter on those websites are also folks who are open or kinky (or both)! Chances are no one is going to give you a hard time about being on a website they are also using.
A nice side effect of some of these sites, particularly FetLife, is it provides a way to learn about local events. You can set up a profile that is mostly anonymous (has no identifying details or face pictures) and then search for in-person events in your area. This will give you the opportunity to go out to casual group events (events where people dress in their normal clothes and act like they would at any other public event) and meet like-mind people. This way you can connect with other people who are looking for similar things without worrying about someone seeing you. Since everyone is dressed normally and on their best behaviour you'll just look like a bunch of friends having coffee or dinner together to anyone who wasn't invited to the group.
A lot of people go to these public events (which are sometimes called munches) as a way to learn from other like-minded people and maybe meet folks they'd like to see again privately at another time. This can be more comfortable than trying to get to know people on-line as you can get an immediate sense of the chemistry you have with people rather than scrolling through profiles and hoping to find a match.