wise man once said---never, never, never turn down food or money when someone offers it to you in kindness. Always take the tips and be gracious and thankful. If someone half-heartedly offers you a tip because of guilt or pressure, or any other reason, politely refuse and let your reward be a job well done.
Owners should split tip only if they participated equally on the job, but really the money should go to the rest of the crew. Owners should be aware of larger tips that go to the crew and verify the money was actually tip money, and not money for additional work or side work (we know this can happen). I have on occasion written a thank you letter to a big tipper and had the crew sign at the bottom, to thank them for their business, and their extra generosity at the end of the job.