Translation:I met your mother and we ate lunch together.
Would "I met with your mother... " be an acceptable translation? In some American English dialects, (at least) there is a slight difference between "met" and "met with". Met, without with, is most commonly used in the context of a first time introduction (like I met him at the party), but met with implies a prearranged meeting (I met with the contractor to discuss the remodeling.) Is there a distinction between the two in Irish? And if so, how would met with be expressed, given that le is already part of the verb.
Bhuail(and its various tenses), I find to be the most problematic word, as it is purely context that decides whether it is hit or meet. What happens if I actually wanted to say "I hit your mother and we ate lunch together?" or something that could just as likely be both meanings such as "I hit/met my brother and then we went home"?
It's not context. It's the le. buail means strike, buail le is a phrasal verb meaning meet.
a common ground between hit and met would be bumped into. Met implies there was a plan but bumped means by chance. So in my opinion bumped into is more correct in this context.
This is not correct. "Buail le" can mean "to meet by chance" or "to meet by arrangement." Checking a dictionary can usually straighten out things like this before you post a question or an opinion on how the language ought to work.. Look at meanings 3, 4, and 5 here: http://www.focloir.ie/ga/dictionary/ei/meet Good luck with your language studies.