Is it possible to have all three at one of the houses?

I've been wanting to marry, but am not sure if this would dismiss my steward, who I enjoy at the house.

yes its possible. at my house at Falkreath, i have my housecarl Rayya, my steward Jordis and my husband Farkas plus my two kids.

Excellent news. Now, I shall get married.

It is possible to have, Housecarl, wife, steward, two children, Armoured huskie and a frostbite spider. When you arrive with a follower and pet it becomes a small army to protect your home.

All this and a bard too.

And you can still have a follower (or two) and an extra horse if you travel with one not from one of the houses. One of my characters travels with Shadowmere when he is not trying to dump her at Lakeview Manor.