Blimey, you’ve had an interesting set of responses!
Ok, so my first thought is that it’s really hard for your brain to jump ahead 2 months in a baby development at this age which makes it REALLY hard to have a clue how you, the baby, separation anxiety or your feeding is going to be.
How close to 6 months will the baby be? You may find you are close to starting on solids which is a whole other thing an harder than the breast/express thing to begin with. Easypeasy after a few weeks but daunting in anticipation like any new stage!
Your baby is more likely to be drinking/eating more in a sitting but in fewer sittings at that stage. Which means both ways could work... you will either need to express bigger but fewer number of bottles or you will be breastfeeding less often but hopefully more efficiently. It also means it’s easier to plan for if you decide to go away alone. You got upset when someone suggested formula - you may well find that formula is the answer in 2 months time regardless of how you plan it. I breastfed one to 17 months, one to 9 months and one to 5 months and not in that order - all weaned to formula or food when they were ready and definitely before I was ready! The 5 month old maybe was not getting what they needed from me but now I know them very well (they are 15 years old!) I now also think they were the type just to get on with the next stage as soon as possible. So just be open to whatever the next 2 months brings. Very hard to plan.
If you take the baby, then you’ve had lots of good advice around pushchair/sling/pop up cots go. Again, remember that the baby will be a lot more robust in 2 months than they feel now. Same goes for sleeping/awake time. I loved taking babies on holiday but personally found the infant stage easier than the on-the-cusp-of-walking and early toddler stage. You will know your own child... if they like some stimulation but are happy in a pushchair/sling and happy to sleep outside then it’s a fab time to take them. If they are a creature of habit who hates change then leaving them home might kindest, even if you aren’t there.
Remember to pack comfort toys, music (if they like that) and easy clothes. Sounds like your friends aren’t going for partying so no need to worry about that. More about the sleep thing. Just try and keep the baby up from 2/3pm onwards for a 7/8pm bedtime or a similar gap at a later time depending on your plans. Take a lavender bath thing too, to encourage sleep.
Ok, that’s all about taking the baby. The next thing to know is that it is ok to go without him. He’s only 3 months old and that is so tiny. You can’t imagine him
Not needing you 34/7. But he will grow so much in the next 2 months and his hourly needs will rightly change and evolve. You may find that you don’t feel as protective or as uncertain without him by then or you may still feel the same. BOTH ARE NORMAL FEELINGS!!!
My personal suggestion is to say yes to the trip but don’t commit either way with the baby. Use the next 2 months to work on the feeding stuff and to get your dh a little more involved here and there on stuff you may unconsciously do yourself every day.
Your friends sound great and they obviously just want you there, baby or not. If that’s the case then make a decision much much nearer the time and enjoy planning Paris shopping AND being with your baby in the meantime.