You should tender as it costs nothinga) You want to ensure the deal goes through...if it doesn't we'll have a 5 cent stock again and forever as the current management is not up to the job (look at what they did do...continued dilution and falling shareprice).
b) AMC management have been around the game a long time, so your GG converted to APM will give you a chance to actually make $$ on your original GG investment.
c) If you tender and a better offer comes along before the deadline (highly unlikely IMO) then your shares can be withdrawn and tendered to the better bid (in fact I think it's automatic).
This is a no brainer!