Try not to worry but I know it isn't that easy! I veer between worrying people will hate it and thinking it is my day they can take it or leave it. My lovely Godmother (and chief wedding planner) said that I should just worry about me and STBDH and people are very welcome not to come or leave at any point - the people that really love us will just be so happy that we are getting married they won't notice anything else.
You are feeding people, giving them drinks and they get to see you get married - I'm sure they will all be having a lovely time. Rain is always a possibility but in April the showers usually blow over quickly - could you get some pretty umbrellas e.g. heart ones for fun photos & shelter?
I would think the kids bags might be best for the meal/speeches when they start to get a bit restless. We are giving out colouring books at the start of the meal.
Enjoy the run up and I wish you a lovely, sunny, stress-free day