The EC directive and the implementing Immigration (EEA) Rules 2016 are both explicit on this question. A parent qualifies as a "family member" for the purposes of deriving freedom of movement rights only if the parent is dependent on the EEA national, who in this case is your son. This is clearly not the case for you.
Bizarrely, you may be able to qualify for an EEA family permit as your son's "extended family member." This is defined in the directive at Article 3, paragraph 2(a), and more precisely and verbosely in the regulations at 8(2):
8.—(1) In these Regulations “extended family member” means a person who is not a family member of an EEA national under regulation 7(1)(a), (b) or (c) and who satisfies a condition in paragraph (2), (3), (4) or (5).
(2) The condition in this paragraph is that the person is—
(a) a relative of an EEA national; and
(b) residing in a country other than the United Kingdom and is dependent upon the EEA national or is a member of the EEA national’s household; and either—
(i) is accompanying the EEA national to the United Kingdom or wants to join the EEA national in the United Kingdom; or
This applies to you because
- you are a relative of your son
- you are a member of your son's household
- you are accompanying your son to the United Kingdom.
This is perhaps a somewhat unusual reading of the definitions, but it's certainly not unreasonable. The best line of attack, should the home office decide to attack, would probably be on the definition of "member of household," which is not defined in the directive or the regulations. For example, they might argue that your son is a member of your household but that the reverse is not true. I do not know whether there is already any case law on this question, or whether the UK has already adopted a policy on non-EEA parents applying for freedom of movement benefits derived from an EEA-national child.
Since the application is free of charge, your best bet is probably to apply for an EEA family permit, explicitly mentioning the "extended family member" reasoning in a cover letter or additional remarks section. Here you would explain that you understand that you do not qualify as a "family member" for the purposes of the regulations because you are not dependent on your son, but you are applying as an "extended family member" because you are members of the same household.
If they refuse the application, you will be able to appeal, to reapply, to apply for a standard visitor visa, or any combination of the three.