Seeking advice for my parents’ investment plan (mid-60s, new $500k inheritance)

Hello all!

My parents are ~65 and probably have another 7–10 years of earning ahead of them. They just inherited ~$500k and want to invest it gradually over the next 12–16 months. They don’t need the money right now and are comfortable with market volatility. Their goal is basically S&P-500-level returns with a little diversification.

They recently opened a Schwab brokerage account and were told by a financial advisor that they “should” sign with him. We’re not sure that’s necessary since they’re leaning toward a simple, low-fee, ETF-based plan and dollar-cost averaging $5–10k per week.

Here’s the rough allocation we’re considering:

U.S. Large Cap (S&P-ish): SCHX – 40%

Total U.S. Market: SCHB – 30%

Developed International: SCHF – 10%

Emerging Markets: SCHE – 5%

U.S. Bonds: SCHZ – 10%

TIPS: SCHP – 5%

All funds have low expense ratios and can be automated at Schwab.

Questions:
1. Does this allocation make sense for people in their mid-60s who don’t need the money immediately?

2. Any pitfalls or nuances with this setup (ETF vs mutual fund, tax considerations, rebalancing, etc.)?

3. Would a simpler one-fund option (like SWANX/SWYNX) be more appropriate?

4. Is hiring a financial advisor here actually necessary, or is this straightforward enough to DIY?

Thanks in advance for any input.