I know that preschoolers are considered "Toddlers" but the middle ages in the Sims always seem to get to me. See toddlers are more like 1-3 years (still drink bottles, sleep in cribs, sit in highchairs, still toddle) then there are preschoolers 3-5 years (Can walk normally, go to daycare for school as a prepration for Elementary school, don't need to sit in high chairs anymore, don't drink out of bottles anymore,) So there is a bit of a difference there. So I was wondering if there is a hack or mod that allows preschoolers? Because there is a difference between a toddler and a preschooler.

There isn't any type of hack, but you can use cc to make older toddlers different from younger ones.

Toddler beds so they can put themselves to bed and get up themselves.
Sippy cups (moonlightdragon)
Booster seat at Affinity sims +Toddler foods from there like scrambled egg.
Different hair and clothes

You can make a daycare in game at a sims house and use Christianlov's transport mirror to bring the toddlers in.

If you want them to be taller use the stretch skeleton cheat.

Make sure of course that they have all the toddler skills

There is somewhere a small toilet potty so it looks like a toilet not a potty. Might be on here.

There's also a toddler eating table, so they can feed themselves mush. http://modthesims.info/d/255132

Well, can you please link me to the download? I found it but I can't find out where to download.

She probably means that you can use various older-looking hairs and clothes to differentiate between the ages. Shorter hairs and cuter clothes for the smallest toddlers, and longer hairs plus clothes that look like they'd ft an older toddler for the older ones. The same trick works on kids (and even babies), too.

What you'd consider older/younger-looking clothes and hairs is up to your taste.

Which one? Join up at Moonlightdragon (which is Simmer22 own site, link in her siggy) look around there and look around Affinity sims, also worth joining.

The Affinity booster seat http://affinitysims.com/forums/topi.../#comment-63318

With clothes, I mean use something like this on young toddlers http://modthesims.info/download.php?t=542306
Something like this on older toddlers http://modthesims.info/download.php?t=520713

Here's the toilet potty https://www.modthesims.info/d/242310

thanks!