Foster kittens - to crate or not

I foster for a local cat rescue, primarily kittens.  I have a litter of 3 6-7 week old kittens that were trapped yesterday.  I don't think they've lived inside before but they aren't too feral yet.  Two of the kittens hiss and hide, but then when we hold them they calm down.  The third kitten is a completely laid back love bug.  

The question is....should I keep these kittens in a crate?  My husband and I always disagree about this. I want to crate them, but hubby thinks this is cruel and doesn't give them the space to run and play.  He wants to keep them loose in our small-ish foster room.  The problem is, they're not litter trained yet and so there are accidents.  I'm guessing the crate with a litter box inside would help them learn to use the litter box?  The crate is a decent size and has one shelf.  I'd like a bigger crate, but this is the largest one the rescue has.  

Crate Pros:

-less chance of accidents outside litter box (?)

-crate is in our living room so kittens can be more exposed to household activities

-kittens not as likely to get into trouble, especially hiding under our radiators

-easy to find them and pick them up for cuddling

-they seem a little less scared

-I can get hanging water bottle and food bowl, leading to hopefully less food messes 

Crate Cons:

-crate is sort of cramped.  The litter box (one of those cardboard boxes for canned food) takes up a lot of space and the kittens hang out in there and get dirty

-kittens could get bored all day with no space to jump and play

-kittens start meowing to be let out and it breaks my heart!

-our own cat can see the kittens, but all she does is hiss a little and walk away

What I really want to do is buy a larger, multilevel crate.  I like some of the ferret crates I see on Amazon, and I figure kittens are about the same size (I wouldn't keep adult cats in there).  But they're expensive ($125 or so) and I have the tendency to make impulse purchases that I later regret.  It's possible I could get reimbursed by the rescue, but they're short on cash anyway.  I'd probably want to just purchase it myself and do a charity tax write-off.

TIA!

It is a dilemma, but I have always crated young fosters, and indeed a mother and her babies. It does help with litter training, even if they get a bit dirty to start with. But once they are calmed down and used to being handled I open the cage door during the day, still within a confined space like a hall or a bathroom, so they can explore, but shut them in the cage at night. This replicates a den in the wild, and gives them the assurance of a safe place. Then later still, you can leave the cage open all the time, move the litter tray outside it, and the kittens will still probably run back there constantly and sleep in it. They do need a safety net and that gives them confidence. If you have a spare bathroom you can also use a shower cabinet as their safe place, easy to clean out every day!

I actually do pretty much the same thing as @JennyR  does except that once I open the cage door I do not shut it again at night (though I do leave the cage there so they can return to  it as they want to), but a variety of solutions can work. You are already doing a lot for them by simply fostering and giving them a safe enviornment in which to develop.  Thank you for helping these cats!

Ha, I always say "they let me play with kittens and they don't even make me pay for it!"   It can be hard work but I love having kittens.  This is the outlet for my maternal instincts since we've decided not to have human children.  

So I decided to buy a 3-tier cat cage on Amazon today, along with various accessories to make it fun for kittens, like ramps, a hammock, and bedding.  I don't want to think about how much it all cost. But kitten season is here and I think it'll get a lot of use.  I can return the one I have to the rescue.  

I decided to get it after reading a lot of reviews from other people who foster for rescues.  And the height of the cage should make my husband feel better about having them in there - different levels for the litter, food and sleep space.