Family of four age range 30-65 travelling to the Isle of Skye in June to hike the Cuillins. We are all competent and able-bodied to accomplish 7-9 hour hill walking, and I suspect that the Cuillin hikes we have planned (Bla Bheinn, Bruach na Frithe) are possible without a guide... but I am wondering if anyone would strongly recommend renting a guide in order to optimize safety, enjoyment, and directions?

I wouldn't think you'd need a guide for either of those. Bruach na Frithe is one of the most popular and there will be other walkers all along your route.

Bla Bheinn is magnificent https://www.walkhighlands.co.uk/munros/bla-bheinn

How long will you be on Skye? Walking on the Isle is VERY weather dependent. Do not attempt either if it is raining, foggy or there are winds. Will you be around long enough to wait it out if necessary?

Thank you for your help! Those two routes did seem less challenging so I am happy to hear confirmation on that. We are on the Isle for 4 days so will (hopefully) be able to wait out any weather.

With 4 full days, your odds will be pretty good. The weather can be (is) very changeable so if it is nasty today tomorrow will likely be better.

I hiked Bla Bhenin some years back, 2006. I was alone so I hired a guide. (My wife turned me loose in the hills, or I turned her loose in town). The trail was basically straightforward, but we walked into dense fog and I doubt I'd have found the actual summit without him. In fact I would have turned back, not a good place to be in thick fog without knowing the area well.

Plus the guide took me down a non-standard route, which was fun. See photo below, he brought his dogs with him. We descended below the clouds back into fantastic scenery.

Then, about a week later we hiked the Five Sisters of Kintail ridge in perfectly clear weather, scattered clouds and warm. Another superb outing, highly recommended if you are looking for more.

So I agree with janisj, you probably don't need the guide if the weather is clear, but either call it off or use a guide if weather is borderline.
Good luck!

Thank you Nelson and janisj for the great advice. One other item that comes to mind is parking... do you know if there are any issues with parking a rental car near the base of these day-hikes? Or in other areas such as the fairy pools?

No parking issues anywhere on Skye really.