Will these be okay for my bike and will they be compatible? I'm planning to buy and get them fitted by a local bike shop.
Also, when replacing chain and cassette is it advisable to also replace the chain ring?
Yes, this cassette and either chain will be fine. You might not need the cassette depending on the condition of your existing chain, but you won't know until you try. Odds are the chainring is fine. Because they are much larger they wear more slowly than cassette sprockets, and in any case the chain engages many teeth so they're more forgiving of wear.
One note- Unless you've already cleared this with the LBS, don't be surprised if they're less than thrilled about installing stuff bought elsewhere. Most shops feel their labor income is only an adjunct to their sales income, and bristle at installing items they haven't sold, especially in the busier months. Some refuse the work altogether, and others charge higher labor rates than they might otherwise.
If you plan on buying online and having an LBS install, you might respect their sensibilities, and bring them the stuff unpackaged, saying you bought them long ago as spares in case they were to be discontinued, and only now need to use them.
You could also add a cassette removal tool, chain tool, and chain whip to your order and do the work yourself. It isn't too difficult of a job.
You've made some great points in your reply, so thank you for that. I will first ask the LBS if they can order the parts, otherwise, I'll order them as planned.
You're probably right about the chainring, after all the chain doesn't shift on it, only on the cassette hence I'd expect more wear and tear on the casette and the chain.
I could, but living in a house with no garage or other workspace makes it difficult, and I'd also need to factor in the cost of a bike stand and possibly a torque wrench.
If you have the room to change a tire at your place, then you have the room to change a cassette. Torque wrench and bike stand not needed. You may still not want to attempt this, that is fine, there are also things I dont want to do myself.