I've read that putting them down in their cot for naps is good because they associate it with sleep, but am worried that dd might start to associate it with shorter naps rather than sleeping through.
That sounds like needlessly worrying about "a rod for your own back" far, far too soon. With my first born I came to realise that trying to avoid The Rod in fact created The Rod.
Bear in mind that your baby will be having daytime naps for a long time, through the baby years and into the toddler years. The reading you have done will be in relation to much older babies.
When you are down to just one lunchtime nap a day (from around 12 months old through to about 3 years old), then it would be important to ensure that is established as happening in a 'place for sleep' (ie cot) so that the sleep/place association develops.
Until our babies are about 6 months it is worth remembering that they are still tiny and young babies. They aren't making associations or bad habits yet. They just need their needs met. Baby needs to sleep - anywhere and anyhow. And full tummies - anyhow.
So if daytime sleeps in the cot works for you - it is convenient having baby in a dark, quiet room - then that is fine. But don't be doing it with any worry about The Rod.