I think it would be much easier to approach ground staff if you want to ride up there for the whole flight ( they can organise it through the captain before boarding).
We are generally very busy during boarding, (greeting, bags, juices, cabin security, cooking etc) - even busier on short sectors - and there will be times when we dont have the time to organise the request.
I think it would be easier to request a visit to the flight deck during flight and then directly request the jump for landing to the techies when you go for a visit.
I think you will also find that jump seat rides/visits for persons who are not employees/ family of the tech crew, will not be allowed in the near future. It is a potential security risk - and all airlines are tightening their security !!