If that Celestron 80mm "guide scope" is the one that's an f/7.5, stay away. Far away. It's poorly made, heavy, and the mounting rings are designed for a Losmandy rail, which if you buy the one from Celestron, will add another several pounds to the setup. At f/7.5 it is also dim, requiring a higher-end guide camera such as the ASI175mm Mini. I don't know what they intended it to be used for, but guiding a small refractor is definitely not it.
I got one for my Celestron 8" f/5 Newtonian scope, back early on when I had to use a 2x Barlow to get my DSLR to focus. I had read the books and dutifully done the math, and with a 2,000mm effective focal length and desiring a 3:1 pixel ratio for the guider, realized that I needed a guide scope with a focal length of at least 480mm. That "guide scope", especially being on sale at the time, seemed to be the right answer. Being stubborn, I made it work, but what a mess...
The real answer was to get a coma corrector for the scope (which I later discovered I needed anyway), and that the slight Barlow effect of the corrector would also solve the DSLR focus issue. That brought the effective focal length for the OTA down to a much more manageable 1,150mm, which put a raft of other, shorter, lighter, and significantly higher quality guide scopes within range. I now have a 130mm f/7 refractor (910mm focal length) and guide it with the ZWO 60mm f/4.6 scope. Much better.
A 30mm guide scope should be ok for your refractor, though I would look for perhaps a slightly larger one for some future proofing. The 30's tend to want to be mounted in the "finder shoe", which can be a source of trouble ("differential flexure"). Try to find one that has two mount points. Keep it centrally mounted, as close to the imaging scope as you can, and in line with the counterweights so that balance is maintained in all directions. That said, if you're careful, and it fits your budget, it's probably going to be fine. We too often recommend the ideal, when taking one step back from perfect is totally good enough.