An appeal process is good but i think it will take ages as far as ive read here and some articles about it....So my advice is should your daughter-in-law go back to the Philippines and apply for a spouse visa because it will be a lot quicker...and as you said your son got his own business meaning he can support his family ,got his place or renting?? and they are legally married...so,no ground for refusal if applied in the Philippines and in correct process this time...goodluck !!