Personally, someone I know would never get kicked for someone better for normal games. If one of my friends wanted to play and I'm playing ranked 5s then I'd tell them I'm busy but if it came down to normal games I'd even kick out higher ranked randoms to make room for them.
In your case though you're bronze 3 and your friends are probably gold. You could very easily improve at 1 specific role to play with them. We all understand that it's better to play with close friends but when you get to the bronze levels, people don't even know what items to buy and that's like the most basic shit. Super annoying having to play with someone who won't even buy the right items, doesn't know when to use abilities, and people who just don't know how to lane and get cs without fighting your opponent and constantly dying.
Just watch some videos or get someone to coach you, plenty of people trying to get into coaching and will do it for free. Getting to gold is very easy, you don't need mechanical skill just game knowledge. If you know enough about the game, you can play Garen (top), warwick or master yi (jungle), Annie (mid), adc is something you need to avoid because there's no such thing as a basic adc champ, and Janna/Soraka (support). Honestly, Janna and Soraka just buff the adc so the adc can do all the work so if you just play those I'm sure your friends wouldn't mind.