Hi, I’m going to clipless pedals for my old Cannondale. I’ve got a set of old PD1056’s I was thinking of using, but also have newer mountain bike style pedals.

I don’t have shoes, and would like to avoid buying more than I need to.

Are the Look pedals safe at this age? Anything to be concerned about?

It looks like the look pedal has a lot of miles left in it yet. As long as the rear clip still pivots correctly and there's no cracks or missing/badly worn out surfaces on it, it should still be OK.
Also check the bearings for binding and drag. Some Look pedals did have problems with their outboard bearings. They are serviceable (with a special tool), but many do not bother and just use them till they fall apart or wear out.

The hazard of the old Look pedals is their "Delta" cleats that offer no lateral traction support while walking.

Ah, a perspective I hadn’t considered! Thanks for this.

Is there benefit to a road style pedal vs. a mtn bike style pedal?

I’ve been riding look pedals/delta cleats since the early 80s. They’re a little slippery but not hazardous. Just walk carefully.

You can also buy cleat covers for Look / compatible cleats for walking, and "pontoons" for SPDs.

I concur with the Busdriver, use the LOOK pedals ,you will be fine. I still run those on all my bikes and have never had an issue.

The Red cleats have a built in feature that allows your foot to float a bit and will aid in preventing knee injuries. Shoes are expensive, buy the Road shoes and leave the MTB pedals for another bike.

The big advantage of road cleats, other than that the road shoes usually have better forefoot sole stiffness, is that the larger road cleats interact with the pedal binding mechanism without needing the shoe tread to contribute to the slop-free binding of the cleat in the pedal.
The mtb cleats rely on the shoe's tread for attachment stability, but the tread begins wearing immediately at the critical contact area with the pedal.
For this and other reasons, the plastic road cleats have a more consistent release action, which better allows both a secure attachment and consistent release. A higher-performing binding in other words.

At least Look has rubber inserts under their cleats to help get a little bit of traction, if you keep your heels up, off the ground, while walking.
I still remeber before the mid 80's, having to walk around on my Diadoras, when racing bike shoes for clipped pedals did not have any rubber traction pads, just 100% slippery plastic soles and cleats and a couple of also very slippery cleat mounting bolts.
Eventually the soles and cleats get beat up enough that you do get a bit of traction.

I use Look Delta and Shimano SPD-SL pedals/cleats. Both with comparable Scott and Fizik road shoes -- rigid soles. Barely suitable for walking regardless of cleats.

Look Delta pros:
I prefer Look for riding. The red Delta cleats have plenty of float, which took some experience to adapt to, but are comfortable overall.
And they're easier to unclip -- very positive feel.
Secure. I've never managed to yank a foot out unintentionally while standing to sprint, including pulling up a lot on the pedals, enough to actually lift the rear wheel off the ground. This is crucial to me. Slipping out of foot retention can lead to a painful encounter between groin and top tube, or a crash.

Cons:
Harder to walk in. Sounds and feels like walking in backward high heels. Slippery on some surfaces. I'm extremely careful about where I put a foot down in traffic.
I find them harder to clip into quickly. Usually takes me 2 or 3 tries, just trying to hook the front of the cleat into the pedal, without looking, from a dead stop while in traffic. PITA.
The float took some time to get used to. Felt like ice skates at first. Now it feels natural.
The generous float also demands more heel pivot to unclip.

Shimano SPD-SL pros:
Easier to clip into.
Easier to walk in. Despite being the same basic type of cleat as Look, the rubber pads make these easier and quieter to walk in, and most secure on more terrain when stopped in traffic.
Like Look Delta, very secure. I haven't managed to unintentionally unclip while standing to sprint while pulling up on the pedals. Theoretically the narrower float might make it possible to unintentionally unclip, but so far this hasn't happened.

Cons:
Unclipping feels a bit mushy compared with the crisp release of Look Delta. The rubber pads and slightly softer cleat material dampen the feel compared with Look Delta.
Less float, so aligning the cleats is more critical. I did a test ride, repeating the same circuit several times, stopping to adjust the cleats on each loop. The circuit mimicked most stuff I'd encounter in a typical ride. I haven't need to re-adjust the cleats since doing this last month.

The differences are pretty minor. Look Delta and Shimano SPD-SL cleats and pedals are very similar overall. I'd be satisfied with either.

I might try mountain bike style clipless with a hybrid for the walkable shoes and two-sided pedals with the option to ride without foot retention. But I'm satisfied with what I have now for my road bikes.

For walking also consider in my experience quality shoe manufacturers make three-bolt soles as rigid as possible for performance, which can make walking a pain. I don't race so SPD or even Crankbrothers are for me.

Fantastic responses, all! Thank you!

I think I may let the shoe be my deciding factor. I also don’t race but would like to up my ride game. I’ll go shoe shopping and see what I find.