The biz plat is a good offer, though you might be able to pull it up via support. Any non-cobranded Amex can support to any Amex card (personal or business). Though supports are a bit weird at the moment, you get 4x spend on the card you supported from. Except if you support from a biz plat, that comes with 15k plus the 4x. So how valuable it is just depends on how much spend you want to put on the card.
If you do decide you want to go through a support, you might need to try different things to pull up the 150k offer. Like different browsers, devices, incognito or not, VPN, etc.
The biz plat won't add to you dad's 5/24 and since he's an existing customer, probably won't even get a hard pull. So it has no bearing on what he's doing with Chase. Probably more a question of when he wants to do the spend.
For the personal plat, this one is probably better if you can maximize the 15x. I think it's not available via support.
https://www.doctorofcredit.com/amer...hop-small-restaurant-for-6-months-resy-offer/