yes, 90 days on entry. plus 60 days extension based on visiting family, makes 150 days. BUT be aware that some Immigration Offices only allow 1 (one) time this 60 day extension during the complete life time of the visa.
IF you have the 1 year Multiple Entry Non Immigrant O visa, you get 90 days of stay, just before the last day, you make a border run to get a new 90 day period.
There is no 30 day Extension of Stay possible on this visa, depending on how long you like to stay inside Thailand, you might ask for a 60 day Extension of Stay to visit family.
NO, a Visa is issued with different dates on it and used to enter Thailand.
You can not renew it. You can apply at a local Immigration Office for an Extension of Stay based on being over 50 years of age, visit the office first to show your passport and visa and ask the hand out with requirements.
Best option is for both the Multiple Entry Non Immigrant O visa, as for the Extension of Stay based on Thai Children you need to have parental rights from family court or Amphuer depending on age of the child.
Just a birth certificate is not enough for an Extension of Stay at Immigration.
No, You arrive at the airport, hand over your passport and get 30 days of stay based on the Visa Exempt Entry.
Then you visit an Immigration Office to apply for a 30 day Extension of Stay based on tourism.
Easier and more convenient is to apply before you even make your way into Thailand for the Single Entry Tourist Visa which gives you directly 60 days on entry and can be extended once at a local Immigration Office with another 30 days.