If the doe is just under 2 pounds and the buck is 3 pounds, it should be okay. But you need to ask yourself if they're good representations of the breed. Just because they're purebred doesn't mean they SHOULD be bred. The breeding should accomplish babies that are also good representations of the breed (and preferably even better quality than the parents, though that's not guaranteed since it's dependent upon how well the bloodlines mesh).
Also, as was mentioned, any time you breed a doe, her life is at risk. It also lowers her life expectancy with each litter she has. I've never had a breeding doe make it past the age of 4 1/2 years.
Also, how old are they? They should be at least 6 months old, but the doe shouldn't be older than 1 year if it's her first litter. You're asking for trouble then. If you do breed, allow the buck to get her several times throughout the day. I never bred if I wasn't going to be home most of the day. The more times he gets her, the bigger the litter size should be. The bigger the litter size, the smaller the babies will be to pass. Hope this helps.