Most retirement portfolios have less than 50% bonds, so it's overly conservative for someone who is still working. If they've ignored their balance this long, maybe they can switch to some stock investments and mostly ignore it?
I think I'd go with 70% (same as yours) S&P 500 index fund, partly for the name brand. If they know "S&P 500" means indexing, and matches the market, that can make it easier for them to understand and stick with the investment. They can also say "S&P 500" to others, and hopefully others understand it's a good idea. Maybe they can leave the other 30% in cash, so the only change they make is 70% S&P 500.
My recommendation is very different in this case versus other situations, because those two friends will have to take a single piece of advice and run with it for months or years. So "S&P 500, with the same 70% as me" [meaning your allocation] would be my suggestion to your friends.