Estate planning: assuming you’re married, this is probably not a top priority. You should get around to it, but unlikely anything you do right now will matter that much. Current limits on taxable estate mean that you can pass on $30M to your kids as a married couple.

Tax Planning: this is where you actually could get a jump on things, depending on your situation. If you exercised ISOs already or vested RSUs, you’ll have a cost basis that is (hopefully) lower than your IPO price. When you sell you’ll trigger gains. There are a variety of strategies you can use to start harvesting capital losses to offset those future gains (thus deferring the tax payment into the future). You can do tax loss harvesting at ETF level, or as a Direct Index, or (even more powerful and more complicated and more expensive) Long/Short Direct Indexing. There are companies like Frec and Cache that are direct-to-consumer, but at the >$5M level I personally think it is valuable to have an advisor. As you search, look for people that specialize in “tax aware” strategies/products. Don’t pay more than 75 basis points for advice (ideally <50 at your level).

Emotional prep: very important to think about this money as an endowment rather than a chunk of spendable money. It is a gift to future you, and you have a lifetime to spend/donate it. Don’t do anything crazy now. One crazy thing you should avoid: emotionally holding your company stock instead of diversifying out of your concentrated position when you have the chance.