SSO
ProShares Ultra S&P500
stock NYSE ETF

If you believe in S&P 500, why not UPRO or SSO as these follow the index?

What you are looking for is either SSO, QQQ or QLD

80% S&P 500 Index Funds. Slightly leveraged (9/10 FXAIX/SPYM/IVV & 1/10 SSO). Considering additional leverage (to be fair, leverage isn't a typical "Boglehead" idea, on the other hand data shows 1.5x to 2.0x leverage historically has better returns for set it and forget it style investing so I don't see it as incompatible)
10% BOXX (taxable accounts only - treasury-like returns but no distributions and no taxes until sold, at least for the time being while IRS reviews)
5% High Yield Bond Funds
5% Funny Money - individual stocks, trying a high yield index fund (HDV)

70 QLD 30 SSO

I've been all in SSO (2x SPY) for over two years now. Up 71% versus 52% for QQQ and 42% for SPY.
I've had A LOT of FOMO over this period but I think this is an underrated and uncomplicated investment strategy for someone with a long investing time frame.

Do VOO/SSO split. Kids can and should take on the added volatility