I would do it at 4pm before you eat to be honest, he will only be having a couple of teaspoons and you don't want solids to interfer with his bedtime bottle.
I had forgotton how old your LO is - he is still very young to be starting solids, as close to 6 months as possible is the general guidelines so I would leave that 2nd meal for a good few weeks - you really don't need to rush things.
Laura