How to spend my son 3rd birthday with my ex

Shannon

So my son is 3 in April, I got a new boyfriend been dating a year now, but I would like to spend my sons birthday with myself his dad and my new partner and of course my ex new partner would be there too. I suggested a farm or zoo if we wasn’t in lockdown if we were then just me my son and his dad but his dad wants me and my boyfriend to come over to his place and celebrate it there which I don’t feel comfortable with as imgoing round my ex’s with his new girlfriend there, he said he would be inviting her family and his family none of my family be there so il be all alone (also with corona about dont think he should be inviting everyone but he knows best apparently) my boyfriend suggested spending half day with my son so in morning we would do something in afternoon his dad does something with him

but I don’t want to do half days, I don’t want to miss out on my little boys birthday. What do I do? Want to make it special for him