The young Magpies host the Red Devils at St. James' Park in their final home league fixture of the season, with the game shown live on NUFC TV as Ben Dawson's side chase automatic promotion to Division One.
Newcastle sit in fourth place on 37 points but could potentially move into top spot with a victory and Longstaff - younger brother of Sean - is hopeful his side can end their impressive form on home soil strongly, with eight wins in their last ten matches in all competitions.
The midfielder told nufc.co.uk: "It will be another big game for us, especially with how the table is looking. We don't want to be dropping any points and need to make sure we put as much pressure on the teams around us.
"It is important to win the games we have left and finish as high as we possibly can to try and get a home draw in the play-offs. Having your own fans supporting us can give you that extra boost and we want to keep the momentum going as we are still in the Premier League Cup (semi-finals).
"We have had a good home campaign and we have wanted to make it very tough for away teams to come to our ground and play. I think we have done that for the majority of this year and when we play Man United, we will want to do the same and take away the three points.
"It will be a bit different to the usual games at Whitley Park. It should be a good watch for those who tune in as Manchester United are a good footballing side. Hopefully, it can be an entertaining match for them but a one that we can win."
Newcastle have played the majority of their home fixtures at Whitley Park but Longstaff is relishing another opportunity of featuring at the club's home stadium, after playing in the Magpies' 5-0 thrashing of Sunderland along with their penalty shoot-out victory over Macclesfield Town in the Checkatrade Trophy.
The teenager has witnessed his sibling, Sean, burst into the first team this term after a string of eye-catching performances at St. James' Park, which the 19-year-old is hoping to achieve himself as he aims to follow in the inspiring footsteps of his older brother.
Longstaff added: "As a team, we always want to show people how good we are as a team and what we are capable of. I believe we have done that this season and when the game arrives, we'll be looking to do that and try to put on a show for the fans who come along to support us.
"Whenever you get a chance to play at St. James' Park, it's always something that you dream of as a young kid. I don't think it matters whether there is 52,000 fans or 2,000 there, it's a ground where I used to go to watch the games and when you get the opportunity to play on the pitch, it's a bit surreal.
"I remember watching Sean make his first start and score his first goal for the first team (against Burnley). You could hear the full crowd cheering and chanting his name. It gives you goosebumps knowing that it is your brother doing that and it definitely spurs you on to go and try to do the same."
