If it's Chiang Mai they are visiting I can only recommend Assist Thai Visa Services Group Co.,Ltd who also offer veru petsonal and cmfortable assistance including car with driver when visiting Immigration offices etc...
Another tip. Something the paper pushers won't usually tell you is that after your first WP (which is valid 1 year) you can extend per 2 year each time. This gives you much more slack when you're renewing non-B in Penang.
Having a WP that is still valid for at least another 8 months is actually a requirement in Penang. If you don't have it you need to take a document from the labour office which states you have requested a WP but i don't know the documents official name and number.
Everybody can get a 2year WP from the second year onwards. Always been like that. The paper pushers dont wat you to know this as it halves their profits.