Speed limit for flap 5 is 250 kt's,I think it's not something to worry on take off.
Unlike classic where is 230 kts.
You can select vnav,but how will you handle the noise procedure,for ex. 1000' N1 ,then 3000' up. You'll have N1 at 400' . Not such a big thing on a 737,but if you want to follow the rules....