Taking dog to the beach

I have a question about older dogs on the beach. I have 2 dogs we are taking on vacay for the first time. One is an active but older Aussie (not concerned with her) and the other is a 17yo chi mix with a grade 4 heart murmur and heartworms (we are doing slow kill method given her age).

My chi mix loves to be outside and is active but tired quickly. I’m nervous about keeping her outside for 4-6 hrs on the beach (under shade of course). I also would feel bad about leaving her at the AirBNB by herself even though she would probably sleep all day.

What do you guys think? I hate having guilt of taking one dog and leaving the other or not taking either one of them.