I'm sorry, but there is so much wrong here I feel compelled to break down ever piece of misinformation you just threw out.
You have invincibility frames and should be going straight through that.
G&W's Up-B does NOT have invincibility frames. In fact, it's the other way around Fox and Falco are the ones with invincibility on shine. When you get caught in your shield by spacie pressure they have a lot tools to lock you in shield stun and catch you in frame traps. You can buffer in dodge rolls or try to catch them miss spacing their moves with grabs or jabs or Up-B but you are at a pretty big disadvantage and you are going to bite the bullet a lot.
The biggest thing you can do to avoid there shield pressure is to stay mobile. Avoid the easy shield pressure starters like Nair or recognize when they are going for it and bail out before it gets going.
keeping those hitboxes out from D-Tilt and F-Smash there's no reason they should be starting a combo on you in the first place.
Slow, stationary moves are the worst against spacies. This moves lock you into one thing for 40+ frames, which is plenty of time for a spacies to react and punish. Falco or Wolf will probably just shoot you and combo the laser into shine or nair. Fox will either use his speed to jump right over the hitboxes and start whaling on the defenseless G&W on the other side, or be content to spend those 40+ racking up chip damage on you.
In fact, you can crouch cancel just about everything they can throw at you anyway.
You can't CC a jump cancel shine, which is the main thing they would be throwing at you.
Staying below them with a platform in between is an easy way to slap them with a N-Air, even through shine.
Nairing a platform is not a thing. The move only hits once and has 20+ frames of cool down. A skilled player would probably shield drop > bair you for that. But even a low level player can punish such a bad option. Chef is the go-to move when it comes to pressuring a platform from below. IHOP a few meat pieces and fast fall it to cover most of their space without being caught in so much lag.
I will say that Nair can be used as a tech chase when the opponent is on a platform. It can cover for long enough to outlast their invincibility in many cases.
Staying at the lower left or right corner of WW will give you cover from any angle a spacie can approach you from.
This whole Wario Ware scenario is over simplifying the options that the spacies have. They aren't just going to run in and impale themselves on your hitboxes. Fox will be dash dancing. And since you have no where to go you will be forced to make a guess and do something about it. You can throw Fsmash or Ftilt, but all he has to do is dash back and when you miss he's going to Nair > Shine. Falco and Wolf will probably shoot you with lasers, but they will do it from a range that you can't just react with bucket, and even if you did manage to bucket the laser they can punish the end lag of bucket just as easily.
Wario Ware in general is not a good stage in these matchups. Low ceilings means Fox will eat you up with Usmash kills at 70% and Falco can be even ruder with Shine > Shine kills. None of the spacies mind the close walls either since that means that they can Side-B to the stage in every recovery scenario. G&W wants big blast zones so he can live as long as possible.
The truth is, you don't want to be directly approaching these characters. G&W's shield pressure game is only so-so, since all of his aerials can be punished OoS, even if they are well spaced. You are much better off trying to bait out their mistake. Make them respect your dash dance by using it with some threatening bacon tosses and Dtilts. Then when they mess up and shield or wiff a move you can punish with grab. Or you can use their misspacing to get in their with G&W's one true piece of shield pressure which is fast fall Chef pan.
Once you have them in your hand Spacies can get blowing up pretty fast. We have chain throws against them and their fall speed keeps them in combo's for a long time. So really maximizing the reward you get for each hit should go a long way to evening the matchup out.
Sorry for the callout @
Shockbound
your intent was good, but your knowledge of this matchup seems to extend solely from playing impatient spacies who aren't willing to bait out G&W's slow, punishable attacks, and are instead more interested in just going in hard.