In a colloquial sense, you can shorten it by asking: "Gusto mong kumain sa labas bukas?" or "Kain tayo bukas?"
Where:
"Gusto mong" - Do you want
"kumain" - to eat
"sa labas" - outside
"bukas" - tomorrow
"Kain" - eat
"tayo" - us, together
"bukas" - tomorrow
People usually guess that when you ask them to eat tomorrow, you would be eating outside like in a restaurant, or elsewhere so you don't really have to ask her if she wants to go out. Or if it's really needed for emphasis, you can ask: "Gusto mong lumabas at kumain bukas?"
Where:
"Gusto mong" - Do you like
"lumabas" - to go out
"at kumain" - and eat
"tomorrow." - bukas
In a formal situation or formal writing, you can use:
"Nais mo bang lumabas at mananghalian bukas?"
Where:
"Nais mo bang" - Do you want ("nais" different from "gusto" /but "gusto" can be both used as "like" or "want" depending on the situation).
"lumabas" - to go out
"at mananghalian" - and have lunch /if you are emphasizing 'lunch' (dinner = maghapunan).
Hope this helps.