Hi Sue (and Greetings Mr Gray 😉 )
Like Bob, I did the old version of this trip (America's Golden West) back in 2010 and think your version of the itinerary looks really great (although, being a bit of a maritime history buff, I did enjoy our couple of nights staying in Long Beach next to Queen Mary).
I also did the old Grand Canyon '3-in1' tour on the West Rim and, more recently, the helicopter tour of the South Rim on the National Parks Tour. I'm so glad you will get a chance to do that because, as Bob said, it is incredible. Tip - watch out for the man made pond below as you fly back to the heliport at the end of the tour because the local moose are very fond of it and you will often see them have a paddle - we saw a huge bull sunning himself in it!
I wouldn't worry too much about missing the boat trip if I were you. It was nice but pretty short and only went about a half mile down the Colorado river and then back. We actually got a little bit longer because members of our group in another boat got stuck on a sand bank coming back and we had to go out to rescue them!
The Skywalk is not that far from Gueno Point. It had only been open about a year when my group went but at the time we only had the option of doing the 3-in-1 or the Skywalk, not both. Members of my group that did it while we were on the boat trip were a bit disappointed because, at the time, people were not allowed to take their own cameras on to the Skywalk and had to pay for 'official' ones if they wanted a souvenir. I don't know if that is still the case.
We were given our picnic lunch boxes at Gueno Point and it really is a super place to stop for a while, eat and take pictures. (I could have done without knowing that the gueno, once mined there, was used to make mascara though....eewww!)
Like Bob, I'm always happy to help if you have any other questions Final tip - if you are staying in San Luis Obispo and there is time, ask your TM if you can have a brief stop at the Madonna Inn. It's nothing to do with the singer - it was founded by a Mr and Mrs Madonna and trust me - it's nuts!
Have a fab time
All the best
Mandy