The problem here is the sudden change from having almost nothing to having $2.5B. If you talked to someone who was well adjusted with $2.0B, another $500M would be no big deal. But going from $0 to $2.5B is too big of a jump.
So run it like a business or an investment, with a budget and goals. No investor would hand a brand new CEO $2.5B... they would ration the funds over time. You could do the same with yourself.
For example, put most of the money into a well managed trust and "give" yourself $250K per year as an allowance. You could bump that amount up each year on a predetermined schedule, but you'll probably hit a point where you don't need more. Set a goal that once you've gotten married you'll have access to a one time "payment" of an additional $500,000, perhaps to buy a new house. (You might be financing part of your house... ironic, but it's all part of not being isolated. And your credit score is kick ass.) You first child is born... bump your annual pay by another $50K for each child while your money manager begins automatically setting aside money for college funds.
In other words, live the comfortable life of a trust fund baby, except that you play the role of both parent and child. You will need a reputable firm to handle the details... reach out to other billionaires for recommendations on who to consider for this critical role.
You will probably die with over $2B in the bank, but so what so long as you are happy and you've led a good life? And if you throw yourself into the world (travel, volunteering, parenting, etc.) you will likely discover a cause that you feel is worth of your largess. Don't look for it... you'll know it when you see it.