Question: Is this encouraged and is it a good thing to do:
Meeting someone before they go hajj or umrah
Meeting someone after they return from hajj or umrah

Answer: Yes most definitely, it is good to meet someone before they go for Hajj or Umrah. If the person travelling goes around to meet family and friends, it’s better. Sayyiduna Umar radiallahu anhu was going for umrah. He came to meet rasullullah sallallahu alayhi wa sallam, who said to him
اشركنا يا اخي في دعاءك
“Dear friend! Remember me in your duas”

Sometimes, the person travelling has many things on his/her mind and is unable to go around, so we should pay them a visit. This way they we can ask one another for forgiveness, request for duas etc.

Similarly meeting someone after they return from Hajj or umrah is recommended .

عن ابن عمر رضي الله عنه قال قال رسول الله صلي الله عليه وسلم إذا لقيت الحاج فسلم عليه و صافحه و مره ان يستغفرلك قبل ان ميدخل بيته فانه مغفور له

It is narrated by Abdullah ibn Umar (radhi Allahu anhu) that Rasulullah (Sallalahu alahi wasallam) said,” When you meet a haaji, (upon his arrival) greet him and shake his hands and request him to do istighfar for you, before he enters his house, for verily he is a forgiven one. (Musnad-Imam Ahmed)

So from this, we see that Rasulullah (Sallalahu alahi wasallam) not only encouraged us to meet that Haaji generally after his return, but rather to actually go and meet a Haaji before he enters his house!