Yes, 2-3 people is going to be overwhelming. I think you need at least 4 to make it sane (once a month) with a manager serving as a backstop. Will Larson endorses the notion of 8 people (https://lethain.com/sizing-engineering-teams/). I would also take a hard look at the seniority of your team to make sure you have engineers who are independent enough to deal with ambiguous questions and debug issues that cut across multiple domains/systems. Runbooks and documentation -- not to mention shadowing are important here too in making sure there is sufficient training and expertise to not have issues escalate to other engineers who are trying to get project work done.

Your estimates are only going to be as good as the work you put into preparing them. I'd encourage you to watch this TED video talk about how the most tallest structures were built by kindergarteners, and the people who did the worst were recent business school graduates. The major reason is that they spent focused on building the plan instead of following the iterative process by learning through prototyping and experimentation.