Whereabouts are you OP? PM me if you like and I will do what I can to help.
I am youth secretary, registrations officer and club welfare officer for a local football club, we have 17 junior teams and we have no end of children wanting to play, but we just cannot accommodate them all.
The FA rules state that league matches are not competitive until U12. League results cannot be published for U11 and below, if they are then the team responsible for publishing the result can be fined. The teams are split into divisions and the results after each game are fed back to the league, who usually re-jig everything in October, December and February. This is to make sure the teams are playing at about the same ability level. Tournament and trophy competitions are allowed to be competitive and results can be published.
There is a limit to how many children can be signed on and registered with the league for each team - it's double the number per side eg. 5v5 you can have 10 signed on, 7v7 you can have 14 signed on. Most coaches sign on fewer players as they want to give a decent amount of game time per player.
Frankly, holding trials for mini soccer teams is utterly ridiculous and speaks volumes about the coaches' egos more than anything else. Up to and including U11, they should be having as close to equal game time as possible, the focus should be on fun and development, learning how to be a team player and enjoying the social aspect of it all. There are too many teams coached by people who have a "win at all costs" mentality and it is so damaging. No club should be telling a child they aren't good enough to play.
However, when it comes to spaces for new players, they are limited as football is such a popular sport. Almost all grassroots football clubs are run entirely by volunteers.
We get several enquiries a week for new players and we hate to turn people away, but we simply don't have the volunteers, the pitch space or the team spaces available for any more, and we are a decent sized club.
It's a big commitment to volunteer - my DH coaches an U11 side, he has 14 players signed on and another 6 training with him. One night a week for training plus a Saturday morning match. Then there's the admin through the week - messages from parents, the club, the league, the opposition, the ref. Sorting out the kick off time and who can play, which pitch, refs fees. Attending managers meetings. Dealing with new enquiries, organising tournament entry, new player registrations and transfers, finding a kit sponsor, ordering kit, getting to the ground early to set the pitches up (goals, respect barrier, technical areas, corner flags, clearing the pitch of rubbish, sticks, dog shit so it's safe for the players) then packing it all away at the end, making sure your players have equal game time, an equal number of starts - it is never-ending.
If your husband is happy to volunteer to coach a side, then look for a local club with a good ethos that encourages equal game time, player development and fun. A good place to start is the FA Playmaker Course - it's free and online and all prospective coaches have to compete it before they can enrol on the Introduction to Coaching Football course (this combines the old level 1, safeguarding and emergency aid course and is now entirely online - it costs £160 but many clubs will cover the cost).
Sorry for the essay, I'm very passionate about grassroots and youth football 