Most definitely have your coworkers taken advantage of your willingness. Be careful with this in the future, as they might make it a habit to abuse of your good intentions with other non-development tasks.
You say you would prefer not to involve your boss if possible, but you also state that your coworkers are unwilling to commit to this tasks (one 0% chance and other 50% chance) so this makes it really difficult to try convince them.
I recommend that you speak with your coworkers in a more serious way: gather with both of them, and tell them your concerns. Try explaining the importance of these tasks in the projects, and that they should be handled by all members of the team, so everyone has a chance to focus on the tasks that they are actually supposed to do. Be sure to think of alternatives to propose, like taking turns or dividing those tasks equally.
If none of this works then it seems there will be no other option but to bring your boss into the problem, so she can sort it out (most probably she will end up dividing tasks equally among you three, but this is only speculation). Even though you may not like this, sometimes telling your boss is the only way to go, so don't feel bad about involving her; you are being polite enough by doing these tasks and also tried your best to persuade your coworkers. You also did good on not recurring to your boss as first resort, as it is better to solve things personally with the ones involved.
Another option to consider is that these non-development tasks may be better handled by someone specifically hired to do so (someone in charge of customer support, integration, etc.), as putting developers to do tasks outside their focus may not be wise, as they will most probably end up overworked. This is something you could mention to your boss, so she can decide if it is worth hiring someone to take on those tasks and enable you and your team to carry on with your dev tasks optimally.
Now, regarding the memes I would not worry or bother much about them as long as they don't escalate or affect your work. It is not rare for coworkers to do these kind of jokes, but you should be aware and know where to draw the line between ok and unacceptable, so your company culture is not damaged by your coworkers getting used to this toxic behavior (similar to the Broken window theory as pointed out by @JuanCarlosOropeza). Again, communication is key here, so if that happens make sure you speak clearly to your coworkers before recurring to other solutions like involving your boss.
Good luck, and I hope these advices help you in your situation.