Father/son Kenya safari in July — planning to bring both 8x42 and 10x50. Sanity check?

Heading to Kenya in July for a safari with my 12-year-old son. I've read a ton of threads here, and the consensus seems to be that there's no single "best" size for safari - which works out great, because I want to buy two pairs anyway.

My plan: an 8x42 for the kid (lighter, wider field of view, more forgiving for shaky hands) and a 10x50 for me (more reach, better light gathering for early morning and dusk drives). Both would be Vortex Diamondback HD:

• 8x42: https://vortexoptics.com/vortex-diamondback-hd-8x42-binoculars.html
• 10x50: https://vortexoptics.com/vortex-diamondback-hd-10x50-binocular.html

A few things I'd love input on:

1. Is the 10x50 overkill for safari, or genuinely useful for distant cats/birds?
2. Would you swap the 10x50 for a 10x42? Am I really getting anything more with the 50?
3. Anyone used the Diamondback HD line specifically on safari - any regrets vs. stepping up to Vipers?