Birds are not as dumb as we think. What I would do is I would get a plastic owl, gargoyle, or anything small to scare the birds. I have an owl and it is working nicely! You may get them at Sams Club,...
Motion activated sprinklers are available and also quite expensive. Electric fence or just an extra tall fence would work, perhaps at less cost. The cheapest solution is probably predator urine...
Grass, like weeds, will invade your garden no matter what you do ! My Ontario garden is to the side of my back yard, and I put a barrier into the ground between the lawn and the garden, and the grass...