Unless you have multiple engineers at max lvl who can make the Jard's Peculiar Energy Source it will take you 15 days per pet and another 30 for the mount.
Most people I know are going for the mount, either because they want it for the themselves or as you said want to sell it.
I guess it depends what you need (money?) or want (mount? pet?). 2 months isn't a lot of time tbh and I can generally see how much ppl are charging for new stuff (mount in this case).
I've already decided to get both pets first, after that I can still bother with the mount if I want.
If you're not to bothered with the pets (simply because they are BoP) you could go for the mount to grab some cash, but keep in mind, you won't be the only one and you might not sell it for as much as u expect. As a long term player for example, I never buy anything "brandnew" from the AH, simply because the prices at the start are just nuts. If I look at the pets from the Timeless Isle atm, they cost around 45k on my server (some close to 100k) which is ridiculous.