So to be clear, I think the original question is what to do if you are expecting enough players for two tables, but not enough show up at start time.
This is my method for handling this in tournament, but it's fully applicable to cash games with random seating as well. I am going to use 9 player tables in my example, but this can be adjusted for 10. (And I will note, I developed this method AFTER having making an ill-fated decision in a tournament expecting 18 players, to draw players to both tables but only 9 had shown up at the start time, and instead of reconsolidating we ended up waiting 15 minutes for the 10th to show up and start with two tables of 5. Ultimately we did have 19 players show and it was the biggest and best event I have hosted.)
Also for the sake of the example, I am going to refer to seating chips and a "pot" for each table. But you can apply these principles to using cards or whatever other device you prefer. Just keep a separate pile for each table.
The first 9 players all draw a seat to table one. Players that draw an even number seat (just 4 players of the original 9) will be moved to the same seat number on table 2 when the 10th player arrives. The 10th player draws a seat from the table 2 pot, which would contain the odd numbered seats for table 2. This gives you two tables of five. (If doing 10-seated tables, I would still only have seats 2,4,6,8 move from table 1 and the 11th player will draw from the table 2 pot containing seats 1,3,5,7,9, and 10.)
As players leave the game put their seat chips back in the appropriate table pot for future draws.
After this, new arrivers draw from the pot for the table with the fewest number of players. If tables are even, new players will draw to the lowest numbered table. (Obviously this will be table 1 in a 2 table situation.)
When you make the decision to close table 2, all of those players can draw from the table 1 pot which would contain those open seats.
You could also expand this notion to any number of tables, just predetermine which seats will move. For a 3 table example, when the 19th player arrives, I would predetermine that players in seats 3 and 9 from table 1 move to table 3 along with seats 1, 5, 7 from table 2 (note none of these players would have started on table 1, so this is still maxing out at one move), the 19th player then draws from the even numbered seats on table 3 giving you a table 1 with 7 players, and tables 2 and 3 with 6 players each.
Gotta be honest, I don't love this. Granted, it's never an issue at my house, because I run one table, but once I settle in, the last thing I would want to do is move to another table (regardless of table quality).
At. Cash game it would suck to have to involuntarily change tables, if you’re stuck for some cash you don’t want to involuntarily have to leave it - conversely if the table then gets juicy because a gambler is trying to win his money back you don’t necessarily want that guy to leave, and you don’t want to leave that situation either.
I get these objections, but the problem is the alternative is to waitlist players if you have 11-12 in the room and 2-3 players aren't gambling until you can start a 5-handed game. I understand there's room for a difference of opinion here, but running two games five- or six-handed seems infinitely better than having willing gamblers waiting around for action. A home game is not like a casino where there is a relatively steadier stream of players, and other amusements, of course.
You can talk all you want about players should never be late, but I don't think any host that wants to fill two tables is turning down players that can't make the start time and the more players active the better. Moving a minority of players to facilitate that, especially if randomly determined fairly, seems a small concession.
And to be blunt, I think cooperation with table movement is inherent in the culture of home games offering multiple tables, and players that object to this I would deem unhelpful to game culture.
Rejoinder:
If you want to do a Table 1 preference for early arrivals, you can still apply this principle. The 1st-5th players that arrive are guaranteed Table 1. The 6th-9th players also join table 1 initially, but will be moved to their same seats on Table 2 when the 10th player arrives. Just make sure to remove occupied seats from the pot for table 2 so future players joining table 2 are drawing from the open seats. (And of course return the seat chips for table 1 to the table 1 pot.)
In this case you can also do "must-move" seating on table 2 such that all new players join table 2 and players from table 2 are moved to table 1 in the order of arrival. (Giving the 6th-9th players the first opportunity to join the "main game.")
Also as host, feel free to grant yourself the privilege of always having seat 1 on table 1 for logistic purposes of staying near the chips and cash. The players that will surround you will still be fully random, so other than being exempt from moving, there's no real advantage.
