Clover can be tackled with Weed-B-Gone CCO (Clover, Chick weed & Oxalis killer). It is very effective. Multiple applications may be necessary. Do not use it after re-seeding though. Weed-B-Gone CCO is not very effective for crab grass control. If you are planning just over seeding, do not use Round-up. It is going to kill all the vegetation including your existing lawn. But if the plan is a total re-do, now is the time to apply Round-up. You can re-seed after two weeks. Round-up don't linger in the soil for more than two weeks.

Thanks . So I can spot weed now and seed in a couple of weeks?

yes, with the weed be gon you can. How much do you have?

Thanks again. used weedbe gone clover and chickweed today.

will use crabgrass killer tomorrow. jim