Would allowing me to visit my son but not telling him I’m his mother a reasonable condition on visitation?

I would recommend abiding by the guardians wishes for this first visit, unless you want to postpone it. The issue would have to be evaluated and perhaps an expert needs to be consulted or perhaps the child will need counseling. It depends on what has happened in the past. You may also need a judge to clarify that the condition imposed by the guardian is not reasonable or not the type of condition contemplated by the Court. If their is a probate counsel that represented the child you may want to contact that attorney for clarification and recommendation.