There are different schools of thought when it comes to rats and baths, but the one downside to giving a young rat a bath is how jumpy they can be. If you were to give them a bath, be VERY careful... Young rat [jumpy] + shampoo [may] = disaster. Just keeping a hold of young rats when they're dry is often tough enough.
I've given young rats a bath when absolutely necessary (surrendered in filthy cages), but at young ages, I always try wiping them down with a baby wipe or a **** cloth.
I have to agree with the suggestion of using a baby wipe versus a full bath.
Babies are wiggly, squirmy, jumpers... if you are washing them over a sink or such the fall could harm them.
Try the baby wipe or a damp wash cloth while sitting on the floor if you really feel they need some freshening up.
As for the smell, what type of bedding are you using?
What are you feeding them?
These two things have a lot to do with odor & the control of odor.
As for the fabric hammocks, shelf liners or blankets you may have in their cage... try to change those out frequently. Anything fabric in the cage will hold the smell of urine & rats really seem to enjoy marinating in their own "perfume".
I've made 3 sets of fabric cage accessories for each cage I have. I switch them out every other day or so, wash & hang to dry.