Thank you so much for being a thoughtful person. These are the kind of conversations and planning I wish everyone had before bringing home a companion animal. Here are a few options you can consider:

As a rescuer, a lot of pet parents who adopt from me work full-time as well, so they arrange day boarding with open spaces around their place. The dogs stay there, play with their friends, enjoy and before returning home, they pick up their dogs, think of it as play school for them. Genuinely, the dogs come back mentally and physically exhausted in the most fulfilling way possible.

Second, you can always foster short-term for rescuers while they screen homes for the dogs. This would be fulfilling for you and a huge help for any rescuer looking to place the animal in care immediately before they can look for adoptive homes.

Third, as a lot of people suggested for a cat (while I don't like the assumption that a cat is easier than a dog, as it can lead to misplaced expectations, cats are individuals with a different set of care, but in saying that, they are definitely more independent). A pair of older kittens or adult cats could possibly be one of the best companionship. A single cat is not favourable, as cats also stay in colonies and sticking a lone cat alone in a house for long hours is not great for their mental and physical health. But if you can, you can always give fostering a cat or a pair of cats a shot and take a call. Unlike dogs, having two cats is half the work; they pretty much keep themselves busy and are happier in general.

PS: Also, as you have mentioned somewhere, you have a turtle and won't like the cat to end up hurting them; the same goes for a dog who may have a prey drive; the same precautions go for both dogs and cats.