This is a tough age for gifted kids I think as a lot public schools (and even camps) have pretty strict age cutoffs. Single age groups can be really difficult for a child who is advanced I think.

It may be helpful to explore activities where there is some age mixing (maybe a Montessori with a 3-6 year old classroom?) or some way where a very bright 3 year old can do activities with older kids. When DS was 3 his friends were mostly 5 year olds.