HELP! I Think Magpies have scared Blue Tits away but I’m now fearing the worst thanks to Google

Hello, I’ve had Blue Tits Nesting in my Garden for about 2 years so I thought I’d put a bird feeder out for them so they had food.
The feeder has attracted Magpies and Eurasian Collared Doves… Wednesday morning I witnessed the Magpie dive bomb the doves when they were on the feeder and knocked it over. I’m really worried about the Blue Tits as the children love watching them from the kitchen window but we haven’t seen them since before I put the feeder out. How do I check on my little birdies without frightening them?