The OP hasn't specified what the intended use will be. Are we're talking about a sporting gun (Trap, Skeet, upland birds, waterfowl, ?) or a home defense weapon ? Or something else ?
If we're talking sporting uses then it's going to be a challenge to find one shotgun that fits 4 different users. Male, female, left & right handed, right eye dominant or left eye dominant, big, little, etc.
If we're talking home defense, regulation of the barrels and choke tubes are probably not going to be a big issues.
I don't think an O/U is going to be an affordable choice for a home defense gun.
For a home defense weapon, a good pump action is hard to beat. You can leave the chamber empty, the safety off and the action unlocked. That gives you a safe gun with at least 4 rounds in the magazine (two more than a double barrel). You can put the gun into use by cycling the action and pulling the trigger, that will be equally as simple for left and right handed users.
A side by side can be used as a home defense weapon but I think it is inferior to a pump action for several reasons. If it has internal hammers it needs to be loaded, with the hammers cocked and the safety on - not a good condition to store a gun in.
External hammers at least allow you to store the gun with the hammers down but you still only have two rounds in the gun.