What Now?:
If someone asked me to come over for dinner, should I have said "well, we're inactive right now, is that still ok with you?".
No. If you like the individual(s), go to dinner. If it's just someone from the congregation who doesn't really give a damn about you personally but wants to 'encourage' someone to 'go back to meetings', tell them you've got other plans.
Should I send a letter or email or text to everyone, advising them of our situation?
Only if you're the kind of person who generally sends letters/emails. There's no need for a 'special' announcement, and such an action to a large number of people will most likely result in almost instant shunning, even without 'official' 'judicial' action. When JWs probe about your situation, try to avoid JW jargon like 'inactive' or other jargon like 'fading'. Keep conversations informal. If they question you about doctrinal views, be honest (which may mean saying nothing, or politely changing the subject), but don't feel compelled to go into any detail, especially if you haven't fully researched things yet and are still forming your views.
The JW mindset is that their religion is 'special' and 'different' to other groups. In reality, you're just not attending religious services anymore (don't use the words 'religious services' with them though).