If you were both going to FIRE, then there is definitely a possible play with a taxable brokerage, because MFJ can get $82k of LTCG at 0% federal tax. The catch is that this is counted after regular income, so any other income up to that amount eats into the opportunity. If your wife wants to keep working, the deal becomes the somewhat less-sweet 15% LTCG bracket.
But even if you are heavy on traditional IRA, it's not that bad. You are withdrawing for your expenses, not taking a paycheck. If child care goes away on FIRE, you are withdrawing roughly $60k. Even if you took at 10% penalty, you would be net 22% tax. And there are plenty of ways to blunt that, too; notably, a Roth conversion ladder.
FIRE at 48 gives you 12 years before you can access your 401k penalty free. You could go down the route of SEPP payments, a Roth conversion ladder, etc. They each are a kind of hoop to jump through to live in this phase of life; see which one seems to fit you best.
I myself FIRE'd at 48, in 2020. I had a mix roughly of 40% tIRA, 30% Roth, and 30% taxable. The mix was not fine tuned, but my strategy was tax diversification: to have a variety of tools in the toolbox, to apply to withdrawals and taxes as the rules change over time. My taxable amount is enough to hold me through to 59 1/2. It seemed a close fit in 2022, but it's comfortable, with a couple years to spare (or a couple big splurges, like a kitchen remodel) as I sit today. I am also doing Roth conversions, primarily focused on soaking up my nonrefundable child tax credits, and balancing ACA subsidies. A side effect is that I am building a Roth ladder, should the taxable fall short, but I don't expect to tap it in this phase. Once the tIRA is the primary source of funding, I will use the Roths again to balance ACA costs, until I reach the age for Medicare. In that phase, though, it will be withdrawals if I need funding, but I am approaching an ACA subsidy cliff.
I came into FIRE with a European severance. That large cash cushion gave me the ultimate flexibility; as I learned my new tax situation by doing, I could have hypothetically had 4 years at $0 income, just living off of cash. There is no optimal strategy that would suggest this, though; for me, I fell into it, but it opened up scenarios to consider--not in a serious attempt to so them, but more to think through the "what if?" possibilities. As you get closer to FIRE, and with the cash you have to invest, you might even think that way, if flexibility brings you more comfort at night than return.
