Sounds like a pretty tricky situation.  Your lab is still young and he has lots of energy and I can understand your concern for your dachshund potentially suffering from a back injury which they are already prone to.    I guess your best bet is going to be encouraging activities that do not require jumping.  Give them some bones to chew.  Take your lab outside and really tire him out so he does not want to jump all over the place.  Anytime you see the jumping you will want to discourage it and offer a different type of activity for them to participate in.